CHG: @ematrix / @piwi fixes for 'hf snoop'

[proxmark3-svn] / armsrc / iso14443a.c

//-----------------------------------------------------------------------------
// Merlok - June 2011, 2012
// Gerhard de Koning Gans - May 2008
// Hagen Fritsch - June 2010
//
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// Routines to support ISO 14443 type A.
//-----------------------------------------------------------------------------

#include "proxmark3.h"
#include "apps.h"
#include "util.h"
#include "string.h"
#include "cmd.h"
#include "iso14443crc.h"
#include "iso14443a.h"
#include "crapto1.h"
#include "mifareutil.h"
#include "BigBuf.h"
static uint32_t iso14a_timeout;
int rsamples = 0;
uint8_t trigger = 0;
// the block number for the ISO14443-4 PCB
static uint8_t iso14_pcb_blocknum = 0;

//
// ISO14443 timing:
//
// minimum time between the start bits of consecutive transfers from reader to tag: 7000 carrier (13.56Mhz) cycles
#define REQUEST_GUARD_TIME (7000/16 + 1)
// minimum time between last modulation of tag and next start bit from reader to tag: 1172 carrier cycles 
#define FRAME_DELAY_TIME_PICC_TO_PCD (1172/16 + 1) 
// bool LastCommandWasRequest = FALSE;

//
// Total delays including SSC-Transfers between ARM and FPGA. These are in carrier clock cycles (1/13,56MHz)
//
// When the PM acts as reader and is receiving tag data, it takes
// 3 ticks delay in the AD converter
// 16 ticks until the modulation detector completes and sets curbit
// 8 ticks until bit_to_arm is assigned from curbit
// 8*16 ticks for the transfer from FPGA to ARM
// 4*16 ticks until we measure the time
// - 8*16 ticks because we measure the time of the previous transfer 
#define DELAY_AIR2ARM_AS_READER (3 + 16 + 8 + 8*16 + 4*16 - 8*16) 

// When the PM acts as a reader and is sending, it takes
// 4*16 ticks until we can write data to the sending hold register
// 8*16 ticks until the SHR is transferred to the Sending Shift Register
// 8 ticks until the first transfer starts
// 8 ticks later the FPGA samples the data
// 1 tick to assign mod_sig_coil
#define DELAY_ARM2AIR_AS_READER (4*16 + 8*16 + 8 + 8 + 1)

// When the PM acts as tag and is receiving it takes
// 2 ticks delay in the RF part (for the first falling edge),
// 3 ticks for the A/D conversion,
// 8 ticks on average until the start of the SSC transfer,
// 8 ticks until the SSC samples the first data
// 7*16 ticks to complete the transfer from FPGA to ARM
// 8 ticks until the next ssp_clk rising edge
// 4*16 ticks until we measure the time 
// - 8*16 ticks because we measure the time of the previous transfer 
#define DELAY_AIR2ARM_AS_TAG (2 + 3 + 8 + 8 + 7*16 + 8 + 4*16 - 8*16)
 
// The FPGA will report its internal sending delay in
uint16_t FpgaSendQueueDelay;
// the 5 first bits are the number of bits buffered in mod_sig_buf
// the last three bits are the remaining ticks/2 after the mod_sig_buf shift
#define DELAY_FPGA_QUEUE (FpgaSendQueueDelay<<1)

// When the PM acts as tag and is sending, it takes
// 4*16 ticks until we can write data to the sending hold register
// 8*16 ticks until the SHR is transferred to the Sending Shift Register
// 8 ticks until the first transfer starts
// 8 ticks later the FPGA samples the data
// + a varying number of ticks in the FPGA Delay Queue (mod_sig_buf)
// + 1 tick to assign mod_sig_coil
#define DELAY_ARM2AIR_AS_TAG (4*16 + 8*16 + 8 + 8 + DELAY_FPGA_QUEUE + 1)

// When the PM acts as sniffer and is receiving tag data, it takes
// 3 ticks A/D conversion
// 14 ticks to complete the modulation detection
// 8 ticks (on average) until the result is stored in to_arm
// + the delays in transferring data - which is the same for
// sniffing reader and tag data and therefore not relevant
#define DELAY_TAG_AIR2ARM_AS_SNIFFER (3 + 14 + 8) 
 
// When the PM acts as sniffer and is receiving reader data, it takes
// 2 ticks delay in analogue RF receiver (for the falling edge of the 
// start bit, which marks the start of the communication)
// 3 ticks A/D conversion
// 8 ticks on average until the data is stored in to_arm.
// + the delays in transferring data - which is the same for
// sniffing reader and tag data and therefore not relevant
#define DELAY_READER_AIR2ARM_AS_SNIFFER (2 + 3 + 8) 

//variables used for timing purposes:
//these are in ssp_clk cycles:
static uint32_t NextTransferTime;
static uint32_t LastTimeProxToAirStart;
static uint32_t LastProxToAirDuration;



// CARD TO READER - manchester
// Sequence D: 11110000 modulation with subcarrier during first half
// Sequence E: 00001111 modulation with subcarrier during second half
// Sequence F: 00000000 no modulation with subcarrier
// READER TO CARD - miller
// Sequence X: 00001100 drop after half a period
// Sequence Y: 00000000 no drop
// Sequence Z: 11000000 drop at start
#define	SEC_D 0xf0
#define	SEC_E 0x0f
#define	SEC_F 0x00
#define	SEC_X 0x0c
#define	SEC_Y 0x00
#define	SEC_Z 0xc0

const uint8_t OddByteParity[256] = {
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
  1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1
};


void iso14a_set_trigger(bool enable) {
	trigger = enable;
}


void iso14a_set_timeout(uint32_t timeout) {
	iso14a_timeout = timeout;
	if(MF_DBGLEVEL >= 3) Dbprintf("ISO14443A Timeout set to %ld (%dms)", iso14a_timeout, iso14a_timeout / 106);
}


void iso14a_set_ATS_timeout(uint8_t *ats) {

	uint8_t tb1;
	uint8_t fwi; 
	uint32_t fwt;
	
	if (ats[0] > 1) {							// there is a format byte T0
		if ((ats[1] & 0x20) == 0x20) {			// there is an interface byte TB(1)
			if ((ats[1] & 0x10) == 0x10) {		// there is an interface byte TA(1) preceding TB(1)
				tb1 = ats[3];
			} else {
				tb1 = ats[2];
			}
			fwi = (tb1 & 0xf0) >> 4;			// frame waiting indicator (FWI)
			fwt = 256 * 16 * (1 << fwi);		// frame waiting time (FWT) in 1/fc
			
			iso14a_set_timeout(fwt/(8*16));
		}
	}
}


//-----------------------------------------------------------------------------
// Generate the parity value for a byte sequence
//
//-----------------------------------------------------------------------------
byte_t oddparity (const byte_t bt)
{
	return OddByteParity[bt];
}

void GetParity(const uint8_t *pbtCmd, uint16_t iLen, uint8_t *par)
{
	uint16_t paritybit_cnt = 0;
	uint16_t paritybyte_cnt = 0;
	uint8_t parityBits = 0;

	for (uint16_t i = 0; i < iLen; i++) {
		// Generate the parity bits
		parityBits |= ((OddByteParity[pbtCmd[i]]) << (7-paritybit_cnt));
		if (paritybit_cnt == 7) {
			par[paritybyte_cnt] = parityBits;	// save 8 Bits parity
			parityBits = 0;						// and advance to next Parity Byte
			paritybyte_cnt++;
			paritybit_cnt = 0;
		} else {
			paritybit_cnt++;
		}
	}

	// save remaining parity bits
	par[paritybyte_cnt] = parityBits;
	
}

void AppendCrc14443a(uint8_t* data, int len)
{
	ComputeCrc14443(CRC_14443_A,data,len,data+len,data+len+1);
}

void AppendCrc14443b(uint8_t* data, int len)
{
	ComputeCrc14443(CRC_14443_B,data,len,data+len,data+len+1);
}


//=============================================================================
// ISO 14443 Type A - Miller decoder
//=============================================================================
// Basics:
// This decoder is used when the PM3 acts as a tag.
// The reader will generate "pauses" by temporarily switching of the field. 
// At the PM3 antenna we will therefore measure a modulated antenna voltage. 
// The FPGA does a comparison with a threshold and would deliver e.g.:
// ........  1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1  .......
// The Miller decoder needs to identify the following sequences:
// 2 (or 3) ticks pause followed by 6 (or 5) ticks unmodulated: 	pause at beginning - Sequence Z ("start of communication" or a "0")
// 8 ticks without a modulation: 									no pause - Sequence Y (a "0" or "end of communication" or "no information")
// 4 ticks unmodulated followed by 2 (or 3) ticks pause:			pause in second half - Sequence X (a "1")
// Note 1: the bitstream may start at any time. We therefore need to sync.
// Note 2: the interpretation of Sequence Y and Z depends on the preceding sequence.
//-----------------------------------------------------------------------------
static tUart Uart;

// Lookup-Table to decide if 4 raw bits are a modulation.
// We accept the following:
// 0001  -   a 3 tick wide pause
// 0011  -   a 2 tick wide pause, or a three tick wide pause shifted left
// 0111  -   a 2 tick wide pause shifted left
// 1001  -   a 2 tick wide pause shifted right
const bool Mod_Miller_LUT[] = {
	FALSE,  TRUE, FALSE, TRUE,  FALSE, FALSE, FALSE, TRUE,
	FALSE,  TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE
};
#define IsMillerModulationNibble1(b) (Mod_Miller_LUT[(b & 0x000000F0) >> 4])
#define IsMillerModulationNibble2(b) (Mod_Miller_LUT[(b & 0x0000000F)])

void UartReset()
{
	Uart.state = STATE_UNSYNCD;
	Uart.bitCount = 0;
	Uart.len = 0;						// number of decoded data bytes
	Uart.parityLen = 0;					// number of decoded parity bytes
	Uart.shiftReg = 0;					// shiftreg to hold decoded data bits
	Uart.parityBits = 0;				// holds 8 parity bits
	Uart.startTime = 0;
	Uart.endTime = 0;
	
	Uart.byteCntMax = 0;
	Uart.posCnt = 0;
	Uart.syncBit = 9999;
}

void UartInit(uint8_t *data, uint8_t *parity)
{
	Uart.output = data;
	Uart.parity = parity;
	Uart.fourBits = 0x00000000;			// clear the buffer for 4 Bits
	UartReset();
}

// use parameter non_real_time to provide a timestamp. Set to 0 if the decoder should measure real time
static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
{

	Uart.fourBits = (Uart.fourBits << 8) | bit;
	
	if (Uart.state == STATE_UNSYNCD) {											// not yet synced
	
		Uart.syncBit = 9999; 													// not set
		
		// 00x11111 2|3 ticks pause followed by 6|5 ticks unmodulated	 	Sequence Z (a "0" or "start of communication")
		// 11111111 8 ticks unmodulation									Sequence Y (a "0" or "end of communication" or "no information")
		// 111100x1 4 ticks unmodulated followed by 2|3 ticks pause			Sequence X (a "1")

		// The start bit is one ore more Sequence Y followed by a Sequence Z (... 11111111 00x11111). We need to distinguish from
		// Sequence X followed by Sequence Y followed by Sequence Z     (111100x1 11111111 00x11111)
		// we therefore look for a ...xx1111 11111111 00x11111xxxxxx... pattern 
		// (12 '1's followed by 2 '0's, eventually followed by another '0', followed by 5 '1's)
		//
#define ISO14443A_STARTBIT_MASK		0x07FFEF80		// mask is    00001111 11111111 1110 1111 10000000
#define ISO14443A_STARTBIT_PATTERN	0x07FF8F80		// pattern is 00001111 11111111 1000 1111 10000000

		if		((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 0)) == ISO14443A_STARTBIT_PATTERN >> 0) Uart.syncBit = 7;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 1)) == ISO14443A_STARTBIT_PATTERN >> 1) Uart.syncBit = 6;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 2)) == ISO14443A_STARTBIT_PATTERN >> 2) Uart.syncBit = 5;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 3)) == ISO14443A_STARTBIT_PATTERN >> 3) Uart.syncBit = 4;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 4)) == ISO14443A_STARTBIT_PATTERN >> 4) Uart.syncBit = 3;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 5)) == ISO14443A_STARTBIT_PATTERN >> 5) Uart.syncBit = 2;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 6)) == ISO14443A_STARTBIT_PATTERN >> 6) Uart.syncBit = 1;
		else if ((Uart.fourBits & (ISO14443A_STARTBIT_MASK >> 7)) == ISO14443A_STARTBIT_PATTERN >> 7) Uart.syncBit = 0;

		if (Uart.syncBit != 9999) {												// found a sync bit
				Uart.startTime = non_real_time?non_real_time:(GetCountSspClk() & 0xfffffff8);
				Uart.startTime -= Uart.syncBit;
				Uart.endTime = Uart.startTime;
				Uart.state = STATE_START_OF_COMMUNICATION;
			}

	} else {

		if (IsMillerModulationNibble1(Uart.fourBits >> Uart.syncBit)) {			
			if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) {		// Modulation in both halves - error
				UartReset();
			} else {															// Modulation in first half = Sequence Z = logic "0"
				if (Uart.state == STATE_MILLER_X) {								// error - must not follow after X
					UartReset();
				} else {
					Uart.bitCount++;
					Uart.shiftReg = (Uart.shiftReg >> 1);						// add a 0 to the shiftreg
					Uart.state = STATE_MILLER_Z;
					Uart.endTime = Uart.startTime + 8*(9*Uart.len + Uart.bitCount + 1) - 6;
					if(Uart.bitCount >= 9) {									// if we decoded a full byte (including parity)
						Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);
						Uart.parityBits <<= 1;									// make room for the parity bit
						Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01);		// store parity bit
						Uart.bitCount = 0;
						Uart.shiftReg = 0;
						if((Uart.len&0x0007) == 0) {							// every 8 data bytes
							Uart.parity[Uart.parityLen++] = Uart.parityBits;	// store 8 parity bits
							Uart.parityBits = 0;
						}
					}
				}
			}
		} else {
			if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) {		// Modulation second half = Sequence X = logic "1"
				Uart.bitCount++;
				Uart.shiftReg = (Uart.shiftReg >> 1) | 0x100;					// add a 1 to the shiftreg
				Uart.state = STATE_MILLER_X;
				Uart.endTime = Uart.startTime + 8*(9*Uart.len + Uart.bitCount + 1) - 2;
				if(Uart.bitCount >= 9) {										// if we decoded a full byte (including parity)
					Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);
					Uart.parityBits <<= 1;										// make room for the new parity bit
					Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01); 			// store parity bit
					Uart.bitCount = 0;
					Uart.shiftReg = 0;
					if ((Uart.len&0x0007) == 0) {								// every 8 data bytes
						Uart.parity[Uart.parityLen++] = Uart.parityBits;		// store 8 parity bits
						Uart.parityBits = 0;
					}
				}
			} else {															// no modulation in both halves - Sequence Y
				if (Uart.state == STATE_MILLER_Z || Uart.state == STATE_MILLER_Y) {	// Y after logic "0" - End of Communication
					Uart.state = STATE_UNSYNCD;
					Uart.bitCount--;											// last "0" was part of EOC sequence
					Uart.shiftReg <<= 1;										// drop it
					if(Uart.bitCount > 0) {										// if we decoded some bits
						Uart.shiftReg >>= (9 - Uart.bitCount);					// right align them
						Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);		// add last byte to the output
						Uart.parityBits <<= 1;									// add a (void) parity bit
						Uart.parityBits <<= (8 - (Uart.len&0x0007));			// left align parity bits
						Uart.parity[Uart.parityLen++] = Uart.parityBits;		// and store it
						return TRUE;
					} else if (Uart.len & 0x0007) {								// there are some parity bits to store
						Uart.parityBits <<= (8 - (Uart.len&0x0007));			// left align remaining parity bits
						Uart.parity[Uart.parityLen++] = Uart.parityBits;		// and store them
					}
					if (Uart.len) {
						return TRUE;											// we are finished with decoding the raw data sequence
					} else {
						UartReset();											// Nothing received - start over
					}
				}
				if (Uart.state == STATE_START_OF_COMMUNICATION) {				// error - must not follow directly after SOC
					UartReset();
				} else {														// a logic "0"
					Uart.bitCount++;
					Uart.shiftReg = (Uart.shiftReg >> 1);						// add a 0 to the shiftreg
					Uart.state = STATE_MILLER_Y;
					if(Uart.bitCount >= 9) {									// if we decoded a full byte (including parity)
						Uart.output[Uart.len++] = (Uart.shiftReg & 0xff);
						Uart.parityBits <<= 1;									// make room for the parity bit
						Uart.parityBits |= ((Uart.shiftReg >> 8) & 0x01); 		// store parity bit
						Uart.bitCount = 0;
						Uart.shiftReg = 0;
						if ((Uart.len&0x0007) == 0) {							// every 8 data bytes
							Uart.parity[Uart.parityLen++] = Uart.parityBits;	// store 8 parity bits
							Uart.parityBits = 0;
						}
					}
				}
			}
		}
			
	} 

    return FALSE;	// not finished yet, need more data
}



//=============================================================================
// ISO 14443 Type A - Manchester decoder
//=============================================================================
// Basics:
// This decoder is used when the PM3 acts as a reader.
// The tag will modulate the reader field by asserting different loads to it. As a consequence, the voltage
// at the reader antenna will be modulated as well. The FPGA detects the modulation for us and would deliver e.g. the following:
// ........ 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .......
// The Manchester decoder needs to identify the following sequences:
// 4 ticks modulated followed by 4 ticks unmodulated: 	Sequence D = 1 (also used as "start of communication")
// 4 ticks unmodulated followed by 4 ticks modulated: 	Sequence E = 0
// 8 ticks unmodulated:									Sequence F = end of communication
// 8 ticks modulated:									A collision. Save the collision position and treat as Sequence D
// Note 1: the bitstream may start at any time. We therefore need to sync.
// Note 2: parameter offset is used to determine the position of the parity bits (required for the anticollision command only)
static tDemod Demod;

// Lookup-Table to decide if 4 raw bits are a modulation.
// We accept three or four "1" in any position
const bool Mod_Manchester_LUT[] = {
	FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, TRUE,
	FALSE, FALSE, FALSE, TRUE,  FALSE, TRUE,  TRUE,  TRUE
};

#define IsManchesterModulationNibble1(b) (Mod_Manchester_LUT[(b & 0x00F0) >> 4])
#define IsManchesterModulationNibble2(b) (Mod_Manchester_LUT[(b & 0x000F)])


void DemodReset()
{
	Demod.state = DEMOD_UNSYNCD;
	Demod.len = 0;						// number of decoded data bytes
	Demod.parityLen = 0;
	Demod.shiftReg = 0;					// shiftreg to hold decoded data bits
	Demod.parityBits = 0;				// 
	Demod.collisionPos = 0;				// Position of collision bit
	Demod.twoBits = 0xffff;				// buffer for 2 Bits
	Demod.highCnt = 0;
	Demod.startTime = 0;
	Demod.endTime = 0;
	
	//
	Demod.bitCount = 0;
	Demod.syncBit = 0xFFFF;
	Demod.samples = 0;
}

void DemodInit(uint8_t *data, uint8_t *parity)
{
	Demod.output = data;
	Demod.parity = parity;
	DemodReset();
}

// use parameter non_real_time to provide a timestamp. Set to 0 if the decoder should measure real time
static RAMFUNC int ManchesterDecoding(uint8_t bit, uint16_t offset, uint32_t non_real_time)
{

	Demod.twoBits = (Demod.twoBits << 8) | bit;
	
	if (Demod.state == DEMOD_UNSYNCD) {

		if (Demod.highCnt < 2) {											// wait for a stable unmodulated signal
			if (Demod.twoBits == 0x0000) {
				Demod.highCnt++;
			} else {
				Demod.highCnt = 0;
			}
		} else {
			Demod.syncBit = 0xFFFF;			// not set
			if 		((Demod.twoBits & 0x7700) == 0x7000) Demod.syncBit = 7; 
			else if ((Demod.twoBits & 0x3B80) == 0x3800) Demod.syncBit = 6;
			else if ((Demod.twoBits & 0x1DC0) == 0x1C00) Demod.syncBit = 5;
			else if ((Demod.twoBits & 0x0EE0) == 0x0E00) Demod.syncBit = 4;
			else if ((Demod.twoBits & 0x0770) == 0x0700) Demod.syncBit = 3;
			else if ((Demod.twoBits & 0x03B8) == 0x0380) Demod.syncBit = 2;
			else if ((Demod.twoBits & 0x01DC) == 0x01C0) Demod.syncBit = 1;
			else if ((Demod.twoBits & 0x00EE) == 0x00E0) Demod.syncBit = 0;
			if (Demod.syncBit != 0xFFFF) {
				Demod.startTime = non_real_time?non_real_time:(GetCountSspClk() & 0xfffffff8);
				Demod.startTime -= Demod.syncBit;
				Demod.bitCount = offset;			// number of decoded data bits
				Demod.state = DEMOD_MANCHESTER_DATA;
			}
		}

	} else {

		if (IsManchesterModulationNibble1(Demod.twoBits >> Demod.syncBit)) {		// modulation in first half
			if (IsManchesterModulationNibble2(Demod.twoBits >> Demod.syncBit)) {	// ... and in second half = collision
				if (!Demod.collisionPos) {
					Demod.collisionPos = (Demod.len << 3) + Demod.bitCount;
				}
			}															// modulation in first half only - Sequence D = 1
			Demod.bitCount++;
			Demod.shiftReg = (Demod.shiftReg >> 1) | 0x100;				// in both cases, add a 1 to the shiftreg
			if(Demod.bitCount == 9) {									// if we decoded a full byte (including parity)
				Demod.output[Demod.len++] = (Demod.shiftReg & 0xff);
				Demod.parityBits <<= 1;									// make room for the parity bit
				Demod.parityBits |= ((Demod.shiftReg >> 8) & 0x01); 	// store parity bit
				Demod.bitCount = 0;
				Demod.shiftReg = 0;
				if((Demod.len&0x0007) == 0) {							// every 8 data bytes
					Demod.parity[Demod.parityLen++] = Demod.parityBits;	// store 8 parity bits
					Demod.parityBits = 0;
				}
			}
			Demod.endTime = Demod.startTime + 8*(9*Demod.len + Demod.bitCount + 1) - 4;
		} else {														// no modulation in first half
			if (IsManchesterModulationNibble2(Demod.twoBits >> Demod.syncBit)) {	// and modulation in second half = Sequence E = 0
				Demod.bitCount++;
				Demod.shiftReg = (Demod.shiftReg >> 1);					// add a 0 to the shiftreg
				if(Demod.bitCount >= 9) {								// if we decoded a full byte (including parity)
					Demod.output[Demod.len++] = (Demod.shiftReg & 0xff);
					Demod.parityBits <<= 1;								// make room for the new parity bit
					Demod.parityBits |= ((Demod.shiftReg >> 8) & 0x01); // store parity bit
					Demod.bitCount = 0;
					Demod.shiftReg = 0;
					if ((Demod.len&0x0007) == 0) {						// every 8 data bytes
						Demod.parity[Demod.parityLen++] = Demod.parityBits;	// store 8 parity bits1
						Demod.parityBits = 0;
					}
				}
				Demod.endTime = Demod.startTime + 8*(9*Demod.len + Demod.bitCount + 1);
			} else {													// no modulation in both halves - End of communication
				if(Demod.bitCount > 0) {								// there are some remaining data bits
					Demod.shiftReg >>= (9 - Demod.bitCount);			// right align the decoded bits
					Demod.output[Demod.len++] = Demod.shiftReg & 0xff;	// and add them to the output
					Demod.parityBits <<= 1;								// add a (void) parity bit
					Demod.parityBits <<= (8 - (Demod.len&0x0007));		// left align remaining parity bits
					Demod.parity[Demod.parityLen++] = Demod.parityBits;	// and store them
					return TRUE;
				} else if (Demod.len & 0x0007) {						// there are some parity bits to store
					Demod.parityBits <<= (8 - (Demod.len&0x0007));		// left align remaining parity bits
					Demod.parity[Demod.parityLen++] = Demod.parityBits;	// and store them
				}
				if (Demod.len) {
					return TRUE;										// we are finished with decoding the raw data sequence
				} else { 												// nothing received. Start over
					DemodReset();
				}
			}
		}
	} 
    return FALSE;	// not finished yet, need more data
}

//=============================================================================
// Finally, a `sniffer' for ISO 14443 Type A
// Both sides of communication!
//=============================================================================

//-----------------------------------------------------------------------------
// Record the sequence of commands sent by the reader to the tag, with
// triggering so that we start recording at the point that the tag is moved
// near the reader.
//-----------------------------------------------------------------------------
void RAMFUNC SniffIso14443a(uint8_t param) {
	// param:
	// bit 0 - trigger from first card answer
	// bit 1 - trigger from first reader 7-bit request
	LEDsoff();

	iso14443a_setup(FPGA_HF_ISO14443A_SNIFFER);
	
	// Allocate memory from BigBuf for some buffers
	// free all previous allocations first
	BigBuf_free();
	
	// init trace buffer
	clear_trace();
	set_tracing(TRUE);
	
	// The command (reader -> tag) that we're receiving.
	uint8_t *receivedCmd = BigBuf_malloc(MAX_FRAME_SIZE);
	uint8_t *receivedCmdPar = BigBuf_malloc(MAX_PARITY_SIZE);
	
	// The response (tag -> reader) that we're receiving.
	uint8_t *receivedResponse = BigBuf_malloc(MAX_FRAME_SIZE);
	uint8_t *receivedResponsePar = BigBuf_malloc(MAX_PARITY_SIZE);
	
	// The DMA buffer, used to stream samples from the FPGA
	uint8_t *dmaBuf = BigBuf_malloc(DMA_BUFFER_SIZE);

	uint8_t *data = dmaBuf;
	uint8_t previous_data = 0;
	int maxDataLen = 0;
	int dataLen = 0;
	bool TagIsActive = FALSE;
	bool ReaderIsActive = FALSE;
	
	// Set up the demodulator for tag -> reader responses.
	DemodInit(receivedResponse, receivedResponsePar);
	
	// Set up the demodulator for the reader -> tag commands
	UartInit(receivedCmd, receivedCmdPar);
	
	// Setup and start DMA.
	FpgaSetupSscDma((uint8_t *)dmaBuf, DMA_BUFFER_SIZE);
	
	// We won't start recording the frames that we acquire until we trigger;
	// a good trigger condition to get started is probably when we see a
	// response from the tag.
	// triggered == FALSE -- to wait first for card
	bool triggered = !(param & 0x03); 
	
	// And now we loop, receiving samples.
	for(uint32_t rsamples = 0; TRUE; ) {

		if(BUTTON_PRESS()) {
			DbpString("cancelled by button");
			break;
		}

		LED_A_ON();
		WDT_HIT();

		int register readBufDataP = data - dmaBuf;
		int register dmaBufDataP = DMA_BUFFER_SIZE - AT91C_BASE_PDC_SSC->PDC_RCR;
		if (readBufDataP <= dmaBufDataP){
			dataLen = dmaBufDataP - readBufDataP;
		} else {
			dataLen = DMA_BUFFER_SIZE - readBufDataP + dmaBufDataP;
		}
		// test for length of buffer
		if(dataLen > maxDataLen) {
			maxDataLen = dataLen;
			if(dataLen > (9 * DMA_BUFFER_SIZE / 10)) {
				Dbprintf("blew circular buffer! dataLen=%d", dataLen);
				break;
			}
		}
		if(dataLen < 1) continue;

		// primary buffer was stopped( <-- we lost data!
		if (!AT91C_BASE_PDC_SSC->PDC_RCR) {
			AT91C_BASE_PDC_SSC->PDC_RPR = (uint32_t) dmaBuf;
			AT91C_BASE_PDC_SSC->PDC_RCR = DMA_BUFFER_SIZE;
			Dbprintf("RxEmpty ERROR!!! data length:%d", dataLen); // temporary
		}
		// secondary buffer sets as primary, secondary buffer was stopped
		if (!AT91C_BASE_PDC_SSC->PDC_RNCR) {
			AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) dmaBuf;
			AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;
		}

		LED_A_OFF();
		
		if (rsamples & 0x01) {				// Need two samples to feed Miller and Manchester-Decoder

			if(!TagIsActive) {		// no need to try decoding reader data if the tag is sending
				uint8_t readerdata = (previous_data & 0xF0) | (*data >> 4);
				if (MillerDecoding(readerdata, (rsamples-1)*4)) {
					LED_C_ON();

					// check - if there is a short 7bit request from reader
					if ((!triggered) && (param & 0x02) && (Uart.len == 1) && (Uart.bitCount == 7)) triggered = TRUE;

					if(triggered) {
						if (!LogTrace(receivedCmd, 
										Uart.len, 
										Uart.startTime*16 - DELAY_READER_AIR2ARM_AS_SNIFFER,
										Uart.endTime*16 - DELAY_READER_AIR2ARM_AS_SNIFFER,
										Uart.parity, 
										TRUE)) break;
					}
					/* And ready to receive another command. */
					UartReset();
					/* And also reset the demod code, which might have been */
					/* false-triggered by the commands from the reader. */
					DemodReset();
					LED_B_OFF();
				}
				ReaderIsActive = (Uart.state != STATE_UNSYNCD);
			}

			if(!ReaderIsActive) {		// no need to try decoding tag data if the reader is sending - and we cannot afford the time
				uint8_t tagdata = (previous_data << 4) | (*data & 0x0F);
				if(ManchesterDecoding(tagdata, 0, (rsamples-1)*4)) {
					LED_B_ON();

					if (!LogTrace(receivedResponse, 
									Demod.len, 
									Demod.startTime*16 - DELAY_TAG_AIR2ARM_AS_SNIFFER, 
									Demod.endTime*16 - DELAY_TAG_AIR2ARM_AS_SNIFFER,
									Demod.parity,
									FALSE)) break;

					if ((!triggered) && (param & 0x01)) triggered = TRUE;

					// And ready to receive another response.
					DemodReset();
					// And reset the Miller decoder including itS (now outdated) input buffer
					UartInit(receivedCmd, receivedCmdPar);

					LED_C_OFF();
				} 
				TagIsActive = (Demod.state != DEMOD_UNSYNCD);
			}
		}

		previous_data = *data;
		rsamples++;
		data++;
		if(data == dmaBuf + DMA_BUFFER_SIZE) {
			data = dmaBuf;
		}
	} // main cycle

	FpgaDisableSscDma();
	LEDsoff();

	Dbprintf("maxDataLen=%d, Uart.state=%x, Uart.len=%d", maxDataLen, Uart.state, Uart.len);
	Dbprintf("traceLen=%d, Uart.output[0]=%08x", BigBuf_get_traceLen(), (uint32_t)Uart.output[0]);
	
	set_tracing(FALSE);	
}

//-----------------------------------------------------------------------------
// Prepare tag messages
//-----------------------------------------------------------------------------
static void CodeIso14443aAsTagPar(const uint8_t *cmd, uint16_t len, uint8_t *parity)
{
	ToSendReset();

	// Correction bit, might be removed when not needed
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(1);  // 1
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	
	// Send startbit
	ToSend[++ToSendMax] = SEC_D;
	LastProxToAirDuration = 8 * ToSendMax - 4;

	for(uint16_t i = 0; i < len; i++) {
		uint8_t b = cmd[i];

		// Data bits
		for(uint16_t j = 0; j < 8; j++) {
			if(b & 1) {
				ToSend[++ToSendMax] = SEC_D;
			} else {
				ToSend[++ToSendMax] = SEC_E;
			}
			b >>= 1;
		}

		// Get the parity bit
		if (parity[i>>3] & (0x80>>(i&0x0007))) {
			ToSend[++ToSendMax] = SEC_D;
			LastProxToAirDuration = 8 * ToSendMax - 4;
		} else {
			ToSend[++ToSendMax] = SEC_E;
			LastProxToAirDuration = 8 * ToSendMax;
		}
	}

	// Send stopbit
	ToSend[++ToSendMax] = SEC_F;

	// Convert from last byte pos to length
	ToSendMax++;
}

static void CodeIso14443aAsTag(const uint8_t *cmd, uint16_t len)
{
	uint8_t par[MAX_PARITY_SIZE];
	
	GetParity(cmd, len, par);
	CodeIso14443aAsTagPar(cmd, len, par);
}


static void Code4bitAnswerAsTag(uint8_t cmd)
{
	int i;

	ToSendReset();

	// Correction bit, might be removed when not needed
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(1);  // 1
	ToSendStuffBit(0);
	ToSendStuffBit(0);
	ToSendStuffBit(0);

	// Send startbit
	ToSend[++ToSendMax] = SEC_D;

	uint8_t b = cmd;
	for(i = 0; i < 4; i++) {
		if(b & 1) {
			ToSend[++ToSendMax] = SEC_D;
			LastProxToAirDuration = 8 * ToSendMax - 4;
		} else {
			ToSend[++ToSendMax] = SEC_E;
			LastProxToAirDuration = 8 * ToSendMax;
		}
		b >>= 1;
	}

	// Send stopbit
	ToSend[++ToSendMax] = SEC_F;

	// Convert from last byte pos to length
	ToSendMax++;
}

//-----------------------------------------------------------------------------
// Wait for commands from reader
// Stop when button is pressed
// Or return TRUE when command is captured
//-----------------------------------------------------------------------------
static int GetIso14443aCommandFromReader(uint8_t *received, uint8_t *parity, int *len)
{
    // Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
    // only, since we are receiving, not transmitting).
    // Signal field is off with the appropriate LED
    LED_D_OFF();
    FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_LISTEN);

    // Now run a `software UART' on the stream of incoming samples.
	UartInit(received, parity);

	// clear RXRDY:
    uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;

    for(;;) {
        WDT_HIT();

        if(BUTTON_PRESS()) return FALSE;
		
        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
            b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
			if(MillerDecoding(b, 0)) {
				*len = Uart.len;
				return TRUE;
			}
 		}
    }
}

static int EmSendCmd14443aRaw(uint8_t *resp, uint16_t respLen, bool correctionNeeded);
int EmSend4bitEx(uint8_t resp, bool correctionNeeded);
int EmSend4bit(uint8_t resp);
int EmSendCmdExPar(uint8_t *resp, uint16_t respLen, bool correctionNeeded, uint8_t *par);
int EmSendCmdEx(uint8_t *resp, uint16_t respLen, bool correctionNeeded);
int EmSendCmd(uint8_t *resp, uint16_t respLen);
int EmSendCmdPar(uint8_t *resp, uint16_t respLen, uint8_t *par);
bool EmLogTrace(uint8_t *reader_data, uint16_t reader_len, uint32_t reader_StartTime, uint32_t reader_EndTime, uint8_t *reader_Parity,
				 uint8_t *tag_data, uint16_t tag_len, uint32_t tag_StartTime, uint32_t tag_EndTime, uint8_t *tag_Parity);

static uint8_t* free_buffer_pointer;

typedef struct {
  uint8_t* response;
  size_t   response_n;
  uint8_t* modulation;
  size_t   modulation_n;
  uint32_t ProxToAirDuration;
} tag_response_info_t;

bool prepare_tag_modulation(tag_response_info_t* response_info, size_t max_buffer_size) {
	// Example response, answer to MIFARE Classic read block will be 16 bytes + 2 CRC = 18 bytes
	// This will need the following byte array for a modulation sequence
	//    144        data bits (18 * 8)
	//     18        parity bits
	//      2        Start and stop
	//      1        Correction bit (Answer in 1172 or 1236 periods, see FPGA)
	//      1        just for the case
	// ----------- +
	//    166 bytes, since every bit that needs to be send costs us a byte
	//
 
 
  // Prepare the tag modulation bits from the message
  CodeIso14443aAsTag(response_info->response,response_info->response_n);
  
  // Make sure we do not exceed the free buffer space
  if (ToSendMax > max_buffer_size) {
    Dbprintf("Out of memory, when modulating bits for tag answer:");
    Dbhexdump(response_info->response_n,response_info->response,false);
    return false;
  }
  
  // Copy the byte array, used for this modulation to the buffer position
  memcpy(response_info->modulation,ToSend,ToSendMax);
  
  // Store the number of bytes that were used for encoding/modulation and the time needed to transfer them
  response_info->modulation_n = ToSendMax;
  response_info->ProxToAirDuration = LastProxToAirDuration;
  
  return true;
}


// "precompile" responses. There are 7 predefined responses with a total of 28 bytes data to transmit.
// Coded responses need one byte per bit to transfer (data, parity, start, stop, correction) 
// 28 * 8 data bits, 28 * 1 parity bits, 7 start bits, 7 stop bits, 7 correction bits
// -> need 273 bytes buffer
// 44 * 8 data bits, 44 * 1 parity bits, 9 start bits, 9 stop bits, 9 correction bits --370
// 47 * 8 data bits, 47 * 1 parity bits, 10 start bits, 10 stop bits, 10 correction bits 
#define ALLOCATED_TAG_MODULATION_BUFFER_SIZE 453 

bool prepare_allocated_tag_modulation(tag_response_info_t* response_info) {
  // Retrieve and store the current buffer index
  response_info->modulation = free_buffer_pointer;
  
  // Determine the maximum size we can use from our buffer
  size_t max_buffer_size = ALLOCATED_TAG_MODULATION_BUFFER_SIZE;
  
  // Forward the prepare tag modulation function to the inner function
  if (prepare_tag_modulation(response_info, max_buffer_size)) {
    // Update the free buffer offset
    free_buffer_pointer += ToSendMax;
    return true;
  } else {
    return false;
  }
}

//-----------------------------------------------------------------------------
// Main loop of simulated tag: receive commands from reader, decide what
// response to send, and send it.
//-----------------------------------------------------------------------------
void SimulateIso14443aTag(int tagType, int flags, byte_t* data)
{
	//Here, we collect UID,NT,AR,NR,UID2,NT2,AR2,NR2
	// This can be used in a reader-only attack.
	// (it can also be retrieved via 'hf 14a list', but hey...
	uint32_t ar_nr_responses[] = {0,0,0,0,0,0,0,0,0,0};
	uint8_t ar_nr_collected = 0;
	
	uint8_t sak;
					
	// PACK response to PWD AUTH for EV1/NTAG
	uint8_t response8[4] =  {0,0,0,0};
	
	// The first response contains the ATQA (note: bytes are transmitted in reverse order).
	uint8_t response1[2] =  {0,0};
	
	switch (tagType) {
		case 1: { // MIFARE Classic
			// Says: I am Mifare 1k - original line
			response1[0] = 0x04;
			response1[1] = 0x00;
			sak = 0x08;
		} break;
		case 2: { // MIFARE Ultralight
			// Says: I am a stupid memory tag, no crypto
			response1[0] = 0x44;
			response1[1] = 0x00;
			sak = 0x00;
		} break;
		case 3: { // MIFARE DESFire
			// Says: I am a DESFire tag, ph33r me
			response1[0] = 0x04;
			response1[1] = 0x03;
			sak = 0x20;
		} break;
		case 4: { // ISO/IEC 14443-4
			// Says: I am a javacard (JCOP)
			response1[0] = 0x04;
			response1[1] = 0x00;
			sak = 0x28;
		} break;
		case 5: { // MIFARE TNP3XXX
			// Says: I am a toy
			response1[0] = 0x01;
			response1[1] = 0x0f;
			sak = 0x01;
		} break;
		case 6: { // MIFARE Mini
			// Says: I am a Mifare Mini, 320b
			response1[0] = 0x44;
			response1[1] = 0x00;
			sak = 0x09;
		} break;
		case 7: { // NTAG?
			// Says: I am a NTAG, 
			response1[0] = 0x44;
			response1[1] = 0x00;
			sak = 0x00;
			// PACK
			response8[0] = 0x80;
			response8[1] = 0x80;
			ComputeCrc14443(CRC_14443_A, response8, 2, &response8[2], &response8[3]);
		} break;		
		default: {
			Dbprintf("Error: unkown tagtype (%d)",tagType);
			return;
		} break;
	}
	
	// The second response contains the (mandatory) first 24 bits of the UID
	uint8_t response2[5] = {0x00};

	// Check if the uid uses the (optional) part
	uint8_t response2a[5] = {0x00};
	
	if (flags & FLAG_7B_UID_IN_DATA) {
		response2[0] = 0x88;
		response2[1] = data[0];
		response2[2] = data[1];
		response2[3] = data[2];

		response2a[0] = data[3];
		response2a[1] = data[4];
		response2a[2] = data[5];
		response2a[3] = data[6]; //??
		response2a[4] = response2a[0] ^ response2a[1] ^ response2a[2] ^ response2a[3];

		// Configure the ATQA and SAK accordingly
		response1[0] |= 0x40;
		sak |= 0x04;
	} else {
		memcpy(response2, data, 4);
		//num_to_bytes(uid_1st,4,response2);
		// Configure the ATQA and SAK accordingly
		response1[0] &= 0xBF;
		sak &= 0xFB;
	}

	// Calculate the BitCountCheck (BCC) for the first 4 bytes of the UID.
	response2[4] = response2[0] ^ response2[1] ^ response2[2] ^ response2[3];

	// Prepare the mandatory SAK (for 4 and 7 byte UID)
	uint8_t response3[3]  = {0x00};
	response3[0] = sak;
	ComputeCrc14443(CRC_14443_A, response3, 1, &response3[1], &response3[2]);

	// Prepare the optional second SAK (for 7 byte UID), drop the cascade bit
	uint8_t response3a[3]  = {0x00};
	response3a[0] = sak & 0xFB;
	ComputeCrc14443(CRC_14443_A, response3a, 1, &response3a[1], &response3a[2]);

	uint8_t response5[] = { 0x00, 0x00, 0x00, 0x00 }; // Very random tag nonce
	uint8_t response6[] = { 0x04, 0x58, 0x80, 0x02, 0x00, 0x00 }; // dummy ATS (pseudo-ATR), answer to RATS: 
	// Format byte = 0x58: FSCI=0x08 (FSC=256), TA(1) and TC(1) present, 
	// TA(1) = 0x80: different divisors not supported, DR = 1, DS = 1
	// TB(1) = not present. Defaults: FWI = 4 (FWT = 256 * 16 * 2^4 * 1/fc = 4833us), SFGI = 0 (SFG = 256 * 16 * 2^0 * 1/fc = 302us)
	// TC(1) = 0x02: CID supported, NAD not supported
	ComputeCrc14443(CRC_14443_A, response6, 4, &response6[4], &response6[5]);

	// Prepare GET_VERSION (different for EV-1 / NTAG)
	//uint8_t response7_EV1[] = {0x00, 0x04, 0x03, 0x01, 0x01, 0x00, 0x0b, 0x03, 0xfd, 0xf7};  //EV1 48bytes VERSION.
	uint8_t response7_NTAG[] = {0x00, 0x04, 0x04, 0x02, 0x01, 0x00, 0x11, 0x03, 0x01, 0x9e}; //NTAG 215
	
	// Prepare CHK_TEARING
	uint8_t response9[] =  {0xBD,0x90,0x3f};
	
	#define TAG_RESPONSE_COUNT 10
	tag_response_info_t responses[TAG_RESPONSE_COUNT] = {
		{ .response = response1,  .response_n = sizeof(response1)  },  // Answer to request - respond with card type
		{ .response = response2,  .response_n = sizeof(response2)  },  // Anticollision cascade1 - respond with uid
		{ .response = response2a, .response_n = sizeof(response2a) },  // Anticollision cascade2 - respond with 2nd half of uid if asked
		{ .response = response3,  .response_n = sizeof(response3)  },  // Acknowledge select - cascade 1
		{ .response = response3a, .response_n = sizeof(response3a) },  // Acknowledge select - cascade 2
		{ .response = response5,  .response_n = sizeof(response5)  },  // Authentication answer (random nonce)
		{ .response = response6,  .response_n = sizeof(response6)  },  // dummy ATS (pseudo-ATR), answer to RATS
		{ .response = response7_NTAG,  .response_n = sizeof(response7_NTAG)  },  // EV1/NTAG GET_VERSION response
		{ .response = response8,   .response_n = sizeof(response8) },  // EV1/NTAG PACK response
		{ .response = response9,   .response_n = sizeof(response9) }  // EV1/NTAG CHK_TEAR response
	};

	// Allocate 512 bytes for the dynamic modulation, created when the reader queries for it
	// Such a response is less time critical, so we can prepare them on the fly
	#define DYNAMIC_RESPONSE_BUFFER_SIZE 64
	#define DYNAMIC_MODULATION_BUFFER_SIZE 512
	uint8_t dynamic_response_buffer[DYNAMIC_RESPONSE_BUFFER_SIZE];
	uint8_t dynamic_modulation_buffer[DYNAMIC_MODULATION_BUFFER_SIZE];
	tag_response_info_t dynamic_response_info = {
		.response = dynamic_response_buffer,
		.response_n = 0,
		.modulation = dynamic_modulation_buffer,
		.modulation_n = 0
	};
  
	// We need to listen to the high-frequency, peak-detected path.
	iso14443a_setup(FPGA_HF_ISO14443A_TAGSIM_LISTEN);

	BigBuf_free_keep_EM();

	// allocate buffers:
	uint8_t *receivedCmd = BigBuf_malloc(MAX_FRAME_SIZE);
	uint8_t *receivedCmdPar = BigBuf_malloc(MAX_PARITY_SIZE);
	free_buffer_pointer = BigBuf_malloc(ALLOCATED_TAG_MODULATION_BUFFER_SIZE);

	// clear trace
	clear_trace();
	set_tracing(TRUE);

	// Prepare the responses of the anticollision phase
	// there will be not enough time to do this at the moment the reader sends it REQA
	for (size_t i=0; i<TAG_RESPONSE_COUNT; i++) {
		prepare_allocated_tag_modulation(&responses[i]);
	}

	int len = 0;

	// To control where we are in the protocol
	int order = 0;
	int lastorder;

	// Just to allow some checks
	int happened = 0;
	int happened2 = 0;
	int cmdsRecvd = 0;

	cmdsRecvd = 0;
	tag_response_info_t* p_response;

	LED_A_ON();
	for(;;) {
		// Clean receive command buffer
		
		if(!GetIso14443aCommandFromReader(receivedCmd, receivedCmdPar, &len)) {
			DbpString("Button press");
			break;
		}

		p_response = NULL;
		
		// Okay, look at the command now.
		lastorder = order;
		if(receivedCmd[0] == 0x26) { // Received a REQUEST
			p_response = &responses[0]; order = 1;
		} else if(receivedCmd[0] == 0x52) { // Received a WAKEUP
			p_response = &responses[0]; order = 6;
		} else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x93) {	// Received request for UID (cascade 1)
			p_response = &responses[1]; order = 2;
		} else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x95) { 	// Received request for UID (cascade 2)
			p_response = &responses[2]; order = 20;
		} else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x93) {	// Received a SELECT (cascade 1)
			p_response = &responses[3]; order = 3;
		} else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x95) {	// Received a SELECT (cascade 2)
			p_response = &responses[4]; order = 30;
		} else if(receivedCmd[0] == 0x30) {	// Received a (plain) READ
			uint8_t block = receivedCmd[1];
			if ( tagType == 7 ) {
				uint16_t start = 4 * block;
				
				/*if ( block < 4 ) {
				    //NTAG 215
					uint8_t blockdata[50] = {
					data[0],data[1],data[2], 0x88 ^ data[0] ^ data[1] ^ data[2],
					data[3],data[4],data[5],data[6],
					data[3] ^ data[4] ^ data[5] ^ data[6],0x48,0x0f,0xe0,
					0xe1,0x10,0x12,0x00,
					0x03,0x00,0xfe,0x00, 
					0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
					0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
					0x00,0x00,0x00,0x00,
					0x00,0x00};
					AppendCrc14443a(blockdata+start, 16);
					EmSendCmdEx( blockdata+start, MAX_MIFARE_FRAME_SIZE, false);
				} else {*/	
					uint8_t emdata[MAX_MIFARE_FRAME_SIZE];
					emlGetMemBt( emdata, start, 16);
					AppendCrc14443a(emdata, 16);
					EmSendCmdEx(emdata, sizeof(emdata), false);				
				//}
				p_response = NULL;
				
			} else {			
				EmSendCmdEx(data+(4*block),16,false);
				// Dbprintf("Read request from reader: %x %x",receivedCmd[0],receivedCmd[1]);
				// We already responded, do not send anything with the EmSendCmd14443aRaw() that is called below
				p_response = NULL;
			}
		} else if(receivedCmd[0] == 0x3A) {	// Received a FAST READ (ranged read) -- just returns all zeros.
				
				uint8_t emdata[MAX_FRAME_SIZE];
				int start =  receivedCmd[1] * 4;
				int len   = (receivedCmd[2] - receivedCmd[1] + 1) * 4;
				emlGetMemBt( emdata, start, len);
				AppendCrc14443a(emdata, len);
				EmSendCmdEx(emdata, len+2, false);				
				p_response = NULL;
				
		} else if(receivedCmd[0] == 0x3C && tagType == 7) {	// Received a READ SIGNATURE -- 
				// ECC data,  taken from a NTAG215 amiibo token. might work. LEN: 32, + 2 crc
				uint8_t data[] = {0x56,0x06,0xa6,0x4f,0x43,0x32,0x53,0x6f,
								  0x43,0xda,0x45,0xd6,0x61,0x38,0xaa,0x1e,
								  0xcf,0xd3,0x61,0x36,0xca,0x5f,0xbb,0x05,
								  0xce,0x21,0x24,0x5b,0xa6,0x7a,0x79,0x07,
								  0x00,0x00};
				AppendCrc14443a(data, sizeof(data)-2);
				EmSendCmdEx(data,sizeof(data),false);
				p_response = NULL;					
		} else if(receivedCmd[0] == 0x39 && tagType == 7) {	// Received a READ COUNTER -- 
				uint8_t data[] =  {0x00,0x00,0x00,0x14,0xa5};
				EmSendCmdEx(data,sizeof(data),false);				
				p_response = NULL;
		} else if(receivedCmd[0] == 0xA5 && tagType == 7) {	// Received a INC COUNTER -- 
			// number of counter
			//uint8_t counter = receivedCmd[1];
			//uint32_t val = bytes_to_num(receivedCmd+2,4);
			
			// send ACK
			uint8_t ack[] = {0x0a};
			EmSendCmdEx(ack,sizeof(ack),false);
			p_response = NULL;
			
		} else if(receivedCmd[0] == 0x3E && tagType == 7) {	// Received a CHECK_TEARING_EVENT -- 
				p_response = &responses[9];				
		} else if(receivedCmd[0] == 0x50) {	// Received a HALT

			if (tracing) {
				LogTrace(receivedCmd, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
			}
			p_response = NULL;
		} else if(receivedCmd[0] == 0x60 || receivedCmd[0] == 0x61) {	// Received an authentication request
					
			if ( tagType == 7 ) {   // IF NTAG /EV1  0x60 == GET_VERSION, not a authentication request.
				p_response = &responses[7];
			} else {
				p_response = &responses[5]; order = 7;
			}
		} else if(receivedCmd[0] == 0xE0) {	// Received a RATS request
			if (tagType == 1 || tagType == 2) {	// RATS not supported
				EmSend4bit(CARD_NACK_NA);
				p_response = NULL;
			} else {
				p_response = &responses[6]; order = 70;
			}
		} else if (order == 7 && len == 8) { // Received {nr] and {ar} (part of authentication)
			if (tracing) {
				LogTrace(receivedCmd, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
			}
			uint32_t nonce = bytes_to_num(response5,4);
			uint32_t nr = bytes_to_num(receivedCmd,4);
			uint32_t ar = bytes_to_num(receivedCmd+4,4);
			//Dbprintf("Auth attempt {nonce}{nr}{ar}: %08x %08x %08x", nonce, nr, ar);

			if(flags & FLAG_NR_AR_ATTACK )
			{
				if(ar_nr_collected < 2){
					// Avoid duplicates... probably not necessary, nr should vary. 
					//if(ar_nr_responses[3] != nr){						
						ar_nr_responses[ar_nr_collected*5]   = 0;
						ar_nr_responses[ar_nr_collected*5+1] = 0;
						ar_nr_responses[ar_nr_collected*5+2] = nonce;
						ar_nr_responses[ar_nr_collected*5+3] = nr;
						ar_nr_responses[ar_nr_collected*5+4] = ar;
						ar_nr_collected++;
					//}
				}			

				if(ar_nr_collected > 1 ) {
				
					if (MF_DBGLEVEL >= 2) {
							Dbprintf("Collected two pairs of AR/NR which can be used to extract keys from reader:");
							Dbprintf("../tools/mfkey/mfkey32 %07x%08x %08x %08x %08x %08x %08x",
								ar_nr_responses[0], // UID1
								ar_nr_responses[1], // UID2
								ar_nr_responses[2], // NT
								ar_nr_responses[3], // AR1
								ar_nr_responses[4], // NR1
								ar_nr_responses[8], // AR2
								ar_nr_responses[9]  // NR2
							);
							Dbprintf("../tools/mfkey/mfkey32v2 %06x%08x %08x %08x %08x %08x %08x %08x",
								ar_nr_responses[0], // UID1
								ar_nr_responses[1], // UID2
								ar_nr_responses[2], // NT1
								ar_nr_responses[3], // AR1
								ar_nr_responses[4], // NR1
								ar_nr_responses[7], // NT2
								ar_nr_responses[8], // AR2
								ar_nr_responses[9]  // NR2
								);
					}
					uint8_t len = ar_nr_collected*5*4;
					cmd_send(CMD_ACK,CMD_SIMULATE_MIFARE_CARD,len,0,&ar_nr_responses,len);
					ar_nr_collected = 0;
					memset(ar_nr_responses, 0x00, len);
				}
			}
		} else if (receivedCmd[0] == 0x1a ) // ULC authentication
		{
			
		}
		else if (receivedCmd[0] == 0x1b) // NTAG / EV-1 authentication
		{
			if ( tagType == 7 ) {
				p_response =  &responses[8]; // PACK response
				uint32_t pwd = bytes_to_num(receivedCmd+1,4);
				
				if ( MF_DBGLEVEL >= 3)  Dbprintf("Auth attempt: %08x", pwd);	
			}
		}
		else {
			// Check for ISO 14443A-4 compliant commands, look at left nibble
			switch (receivedCmd[0]) {
				case 0x02:
				case 0x03: {  // IBlock (command no CID)
					dynamic_response_info.response[0] = receivedCmd[0];
					dynamic_response_info.response[1] = 0x90;
					dynamic_response_info.response[2] = 0x00;
					dynamic_response_info.response_n = 3;
				} break;
				case 0x0B:
				case 0x0A: { // IBlock (command CID)
				  dynamic_response_info.response[0] = receivedCmd[0];
				  dynamic_response_info.response[1] = 0x00;
				  dynamic_response_info.response[2] = 0x90;
				  dynamic_response_info.response[3] = 0x00;
				  dynamic_response_info.response_n = 4;
				} break;

				case 0x1A:
				case 0x1B: { // Chaining command
				  dynamic_response_info.response[0] = 0xaa | ((receivedCmd[0]) & 1);
				  dynamic_response_info.response_n = 2;
				} break;

				case 0xaa:
				case 0xbb: {
				  dynamic_response_info.response[0] = receivedCmd[0] ^ 0x11;
				  dynamic_response_info.response_n = 2;
				} break;
				  
				case 0xBA: { // ping / pong
					dynamic_response_info.response[0] = 0xAB;
					dynamic_response_info.response[1] = 0x00;
					dynamic_response_info.response_n = 2;
				} break;

				case 0xCA:
				case 0xC2: { // Readers sends deselect command
					dynamic_response_info.response[0] = 0xCA;
					dynamic_response_info.response[1] = 0x00;
					dynamic_response_info.response_n = 2;
				} break;

				default: {
					// Never seen this command before
					if (tracing) {
						LogTrace(receivedCmd, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					}
					Dbprintf("Received unknown command (len=%d):",len);
					Dbhexdump(len,receivedCmd,false);
					// Do not respond
					dynamic_response_info.response_n = 0;
				} break;
			}
      
			if (dynamic_response_info.response_n > 0) {
				// Copy the CID from the reader query
				dynamic_response_info.response[1] = receivedCmd[1];

				// Add CRC bytes, always used in ISO 14443A-4 compliant cards
				AppendCrc14443a(dynamic_response_info.response,dynamic_response_info.response_n);
				dynamic_response_info.response_n += 2;
        
				if (prepare_tag_modulation(&dynamic_response_info,DYNAMIC_MODULATION_BUFFER_SIZE) == false) {
					Dbprintf("Error preparing tag response");
					if (tracing) {
						LogTrace(receivedCmd, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					}
					break;
				}
				p_response = &dynamic_response_info;
			}
		}

		// Count number of wakeups received after a halt
		if(order == 6 && lastorder == 5) { happened++; }

		// Count number of other messages after a halt
		if(order != 6 && lastorder == 5) { happened2++; }

		if(cmdsRecvd > 999) {
			DbpString("1000 commands later...");
			break;
		}
		cmdsRecvd++;

		if (p_response != NULL) {
			EmSendCmd14443aRaw(p_response->modulation, p_response->modulation_n, receivedCmd[0] == 0x52);
			// do the tracing for the previous reader request and this tag answer:
			uint8_t par[MAX_PARITY_SIZE];
			GetParity(p_response->response, p_response->response_n, par);
	
			EmLogTrace(Uart.output, 
						Uart.len, 
						Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, 
						Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, 
						Uart.parity,
						p_response->response, 
						p_response->response_n,
						LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_TAG,
						(LastTimeProxToAirStart + p_response->ProxToAirDuration)*16 + DELAY_ARM2AIR_AS_TAG, 
						par);
		}
		
		if (!tracing) {
			Dbprintf("Trace Full. Simulation stopped.");
			break;
		}
	}

	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	set_tracing(FALSE);
	BigBuf_free_keep_EM();
	LED_A_OFF();
	
	if (MF_DBGLEVEL >= 4){
		Dbprintf("-[ Wake ups after halt [%d]", happened);
		Dbprintf("-[ Messages after halt [%d]", happened2);
		Dbprintf("-[ Num of received cmd [%d]", cmdsRecvd);
	}
}


// prepare a delayed transfer. This simply shifts ToSend[] by a number
// of bits specified in the delay parameter.
void PrepareDelayedTransfer(uint16_t delay)
{
	uint8_t bitmask = 0;
	uint8_t bits_to_shift = 0;
	uint8_t bits_shifted = 0;

	delay &= 0x07;
	if (delay) {
		for (uint16_t i = 0; i < delay; i++) {
			bitmask |= (0x01 << i);
		}
		ToSend[ToSendMax++] = 0x00;
		for (uint16_t i = 0; i < ToSendMax; i++) {
			bits_to_shift = ToSend[i] & bitmask;
			ToSend[i] = ToSend[i] >> delay;
			ToSend[i] = ToSend[i] | (bits_shifted << (8 - delay));
			bits_shifted = bits_to_shift;
		}
	}
}


//-------------------------------------------------------------------------------------
// Transmit the command (to the tag) that was placed in ToSend[].
// Parameter timing:
// if NULL: transfer at next possible time, taking into account
// 			request guard time and frame delay time
// if == 0:	transfer immediately and return time of transfer
// if != 0: delay transfer until time specified
//-------------------------------------------------------------------------------------
static void TransmitFor14443a(const uint8_t *cmd, uint16_t len, uint32_t *timing)
{
	
	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);

	uint32_t ThisTransferTime = 0;

	if (timing) {
		if(*timing == 0) {										// Measure time
			*timing = (GetCountSspClk() + 8) & 0xfffffff8;
		} else {
			PrepareDelayedTransfer(*timing & 0x00000007);		// Delay transfer (fine tuning - up to 7 MF clock ticks)
		}
		if(MF_DBGLEVEL >= 4 && GetCountSspClk() >= (*timing & 0xfffffff8)) Dbprintf("TransmitFor14443a: Missed timing");
		while(GetCountSspClk() < (*timing & 0xfffffff8));		// Delay transfer (multiple of 8 MF clock ticks)
		LastTimeProxToAirStart = *timing;
	} else {
		ThisTransferTime = ((MAX(NextTransferTime, GetCountSspClk()) & 0xfffffff8) + 8);
		while(GetCountSspClk() < ThisTransferTime);
		LastTimeProxToAirStart = ThisTransferTime;
	}
	
	// clear TXRDY
	AT91C_BASE_SSC->SSC_THR = SEC_Y;

	uint16_t c = 0;
	for(;;) {
		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
			AT91C_BASE_SSC->SSC_THR = cmd[c];
			c++;
			if(c >= len) {
				break;
			}
		}
	}
	
	NextTransferTime = MAX(NextTransferTime, LastTimeProxToAirStart + REQUEST_GUARD_TIME);
}


//-----------------------------------------------------------------------------
// Prepare reader command (in bits, support short frames) to send to FPGA
//-----------------------------------------------------------------------------
void CodeIso14443aBitsAsReaderPar(const uint8_t *cmd, uint16_t bits, const uint8_t *parity)
{
	int i, j;
	int last;
	uint8_t b;

	ToSendReset();

	// Start of Communication (Seq. Z)
	ToSend[++ToSendMax] = SEC_Z;
	LastProxToAirDuration = 8 * (ToSendMax+1) - 6;
	last = 0;

	size_t bytecount = nbytes(bits);
	// Generate send structure for the data bits
	for (i = 0; i < bytecount; i++) {
		// Get the current byte to send
		b = cmd[i];
		size_t bitsleft = MIN((bits-(i*8)),8);

		for (j = 0; j < bitsleft; j++) {
			if (b & 1) {
				// Sequence X
				ToSend[++ToSendMax] = SEC_X;
				LastProxToAirDuration = 8 * (ToSendMax+1) - 2;
				last = 1;
			} else {
				if (last == 0) {
				// Sequence Z
				ToSend[++ToSendMax] = SEC_Z;
				LastProxToAirDuration = 8 * (ToSendMax+1) - 6;
				} else {
					// Sequence Y
					ToSend[++ToSendMax] = SEC_Y;
					last = 0;
				}
			}
			b >>= 1;
		}

		// Only transmit parity bit if we transmitted a complete byte
		if (j == 8 && parity != NULL) {
			// Get the parity bit
			if (parity[i>>3] & (0x80 >> (i&0x0007))) {
				// Sequence X
				ToSend[++ToSendMax] = SEC_X;
				LastProxToAirDuration = 8 * (ToSendMax+1) - 2;
				last = 1;
			} else {
				if (last == 0) {
					// Sequence Z
					ToSend[++ToSendMax] = SEC_Z;
					LastProxToAirDuration = 8 * (ToSendMax+1) - 6;
				} else {
					// Sequence Y
					ToSend[++ToSendMax] = SEC_Y;
					last = 0;
				}
			}
		}
	}

	// End of Communication: Logic 0 followed by Sequence Y
	if (last == 0) {
		// Sequence Z
		ToSend[++ToSendMax] = SEC_Z;
		LastProxToAirDuration = 8 * (ToSendMax+1) - 6;
	} else {
		// Sequence Y
		ToSend[++ToSendMax] = SEC_Y;
		last = 0;
	}
	ToSend[++ToSendMax] = SEC_Y;

	// Convert to length of command:
	ToSendMax++;
}

//-----------------------------------------------------------------------------
// Prepare reader command to send to FPGA
//-----------------------------------------------------------------------------
void CodeIso14443aAsReaderPar(const uint8_t *cmd, uint16_t len, const uint8_t *parity)
{
  CodeIso14443aBitsAsReaderPar(cmd, len*8, parity);
}


//-----------------------------------------------------------------------------
// Wait for commands from reader
// Stop when button is pressed (return 1) or field was gone (return 2)
// Or return 0 when command is captured
//-----------------------------------------------------------------------------
static int EmGetCmd(uint8_t *received, uint16_t *len, uint8_t *parity)
{
	*len = 0;

	uint32_t timer = 0, vtime = 0;
	int analogCnt = 0;
	int analogAVG = 0;

	// Set FPGA mode to "simulated ISO 14443 tag", no modulation (listen
	// only, since we are receiving, not transmitting).
	// Signal field is off with the appropriate LED
	LED_D_OFF();
	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_LISTEN);

	// Set ADC to read field strength
	AT91C_BASE_ADC->ADC_CR = AT91C_ADC_SWRST;
	AT91C_BASE_ADC->ADC_MR =
				ADC_MODE_PRESCALE(63) |
				ADC_MODE_STARTUP_TIME(1) |
				ADC_MODE_SAMPLE_HOLD_TIME(15);
	AT91C_BASE_ADC->ADC_CHER = ADC_CHANNEL(ADC_CHAN_HF);
	// start ADC
	AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
	
	// Now run a 'software UART' on the stream of incoming samples.
	UartInit(received, parity);

	// Clear RXRDY:
    uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
	
	for(;;) {
		WDT_HIT();

		if (BUTTON_PRESS()) return 1;

		// test if the field exists
		if (AT91C_BASE_ADC->ADC_SR & ADC_END_OF_CONVERSION(ADC_CHAN_HF)) {
			analogCnt++;
			analogAVG += AT91C_BASE_ADC->ADC_CDR[ADC_CHAN_HF];
			AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
			if (analogCnt >= 32) {
				if ((MAX_ADC_HF_VOLTAGE * (analogAVG / analogCnt) >> 10) < MF_MINFIELDV) {
					vtime = GetTickCount();
					if (!timer) timer = vtime;
					// 50ms no field --> card to idle state
					if (vtime - timer > 50) return 2;
				} else
					if (timer) timer = 0;
				analogCnt = 0;
				analogAVG = 0;
			}
		}

		// receive and test the miller decoding
        if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
            b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
			if(MillerDecoding(b, 0)) {
				*len = Uart.len;
				return 0;
			}
        }

	}
}


static int EmSendCmd14443aRaw(uint8_t *resp, uint16_t respLen, bool correctionNeeded)
{
	uint8_t b;
	uint16_t i = 0;
	uint32_t ThisTransferTime;
	
	// Modulate Manchester
	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_MOD);

	// include correction bit if necessary
	if (Uart.parityBits & 0x01) {
		correctionNeeded = TRUE;
	}
	if(correctionNeeded) {
		// 1236, so correction bit needed
		i = 0;
	} else {
		i = 1;
	}

 	// clear receiving shift register and holding register
	while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
	b = AT91C_BASE_SSC->SSC_RHR; (void) b;
	while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
	b = AT91C_BASE_SSC->SSC_RHR; (void) b;
	
	// wait for the FPGA to signal fdt_indicator == 1 (the FPGA is ready to queue new data in its delay line)
	for (uint16_t j = 0; j < 5; j++) {	// allow timeout - better late than never
		while(!(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY));
		if (AT91C_BASE_SSC->SSC_RHR) break;
	}

	while ((ThisTransferTime = GetCountSspClk()) & 0x00000007);

	// Clear TXRDY:
	AT91C_BASE_SSC->SSC_THR = SEC_F;

	// send cycle
	for(; i < respLen; ) {
		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
			AT91C_BASE_SSC->SSC_THR = resp[i++];
			FpgaSendQueueDelay = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
		}
	
		if(BUTTON_PRESS()) break;
	}

	// Ensure that the FPGA Delay Queue is empty before we switch to TAGSIM_LISTEN again:
	uint8_t fpga_queued_bits = FpgaSendQueueDelay >> 3;
	for (i = 0; i <= fpga_queued_bits/8 + 1; ) {
		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
			AT91C_BASE_SSC->SSC_THR = SEC_F;
			FpgaSendQueueDelay = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
			i++;
		}
	}

	LastTimeProxToAirStart = ThisTransferTime + (correctionNeeded?8:0);

	return 0;
}

int EmSend4bitEx(uint8_t resp, bool correctionNeeded){
	Code4bitAnswerAsTag(resp);
	int res = EmSendCmd14443aRaw(ToSend, ToSendMax, correctionNeeded);
	// do the tracing for the previous reader request and this tag answer:
	uint8_t par[1];
	GetParity(&resp, 1, par);
	EmLogTrace(Uart.output, 
				Uart.len, 
				Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, 
				Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, 
				Uart.parity,
				&resp, 
				1, 
				LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_TAG,
				(LastTimeProxToAirStart + LastProxToAirDuration)*16 + DELAY_ARM2AIR_AS_TAG, 
				par);
	return res;
}

int EmSend4bit(uint8_t resp){
	return EmSend4bitEx(resp, false);
}

int EmSendCmdExPar(uint8_t *resp, uint16_t respLen, bool correctionNeeded, uint8_t *par){
	CodeIso14443aAsTagPar(resp, respLen, par);
	int res = EmSendCmd14443aRaw(ToSend, ToSendMax, correctionNeeded);
	// do the tracing for the previous reader request and this tag answer:
	EmLogTrace(Uart.output, 
				Uart.len, 
				Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, 
				Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, 
				Uart.parity,
				resp, 
				respLen, 
				LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_TAG,
				(LastTimeProxToAirStart + LastProxToAirDuration)*16 + DELAY_ARM2AIR_AS_TAG, 
				par);
	return res;
}

int EmSendCmdEx(uint8_t *resp, uint16_t respLen, bool correctionNeeded){
	uint8_t par[MAX_PARITY_SIZE];
	GetParity(resp, respLen, par);
	return EmSendCmdExPar(resp, respLen, correctionNeeded, par);
}

int EmSendCmd(uint8_t *resp, uint16_t respLen){
	uint8_t par[MAX_PARITY_SIZE];
	GetParity(resp, respLen, par);
	return EmSendCmdExPar(resp, respLen, false, par);
}

int EmSendCmdPar(uint8_t *resp, uint16_t respLen, uint8_t *par){
	return EmSendCmdExPar(resp, respLen, false, par);
}

bool EmLogTrace(uint8_t *reader_data, uint16_t reader_len, uint32_t reader_StartTime, uint32_t reader_EndTime, uint8_t *reader_Parity,
				 uint8_t *tag_data, uint16_t tag_len, uint32_t tag_StartTime, uint32_t tag_EndTime, uint8_t *tag_Parity)
{
	if (tracing) {
		// we cannot exactly measure the end and start of a received command from reader. However we know that the delay from
		// end of the received command to start of the tag's (simulated by us) answer is n*128+20 or n*128+84 resp.
		// with n >= 9. The start of the tags answer can be measured and therefore the end of the received command be calculated:
		uint16_t reader_modlen = reader_EndTime - reader_StartTime;
		uint16_t approx_fdt = tag_StartTime - reader_EndTime;
		uint16_t exact_fdt = (approx_fdt - 20 + 32)/64 * 64 + 20;
		reader_EndTime = tag_StartTime - exact_fdt;
		reader_StartTime = reader_EndTime - reader_modlen;
		if (!LogTrace(reader_data, reader_len, reader_StartTime, reader_EndTime, reader_Parity, TRUE)) {
			return FALSE;
		} else return(!LogTrace(tag_data, tag_len, tag_StartTime, tag_EndTime, tag_Parity, FALSE));
	} else {
		return TRUE;
	}
}

//-----------------------------------------------------------------------------
// Wait a certain time for tag response
//  If a response is captured return TRUE
//  If it takes too long return FALSE
//-----------------------------------------------------------------------------
static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receivedResponsePar, uint16_t offset)
{
	uint32_t c = 0x00;
	
	// Set FPGA mode to "reader listen mode", no modulation (listen
	// only, since we are receiving, not transmitting).
	// Signal field is on with the appropriate LED
	LED_D_ON();
	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_LISTEN);
	
	// Now get the answer from the card
	DemodInit(receivedResponse, receivedResponsePar);

	// clear RXRDY:
    uint8_t b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;

	for(;;) {
		WDT_HIT();

		if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
			b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
			if(ManchesterDecoding(b, offset, 0)) {
				NextTransferTime = MAX(NextTransferTime, Demod.endTime - (DELAY_AIR2ARM_AS_READER + DELAY_ARM2AIR_AS_READER)/16 + FRAME_DELAY_TIME_PICC_TO_PCD);
				return TRUE;
			} else if (c++ > iso14a_timeout && Demod.state == DEMOD_UNSYNCD) {
				return FALSE; 
			}
		}
	}
}

void ReaderTransmitBitsPar(uint8_t* frame, uint16_t bits, uint8_t *par, uint32_t *timing)
{
	CodeIso14443aBitsAsReaderPar(frame, bits, par);
  
	// Send command to tag
	TransmitFor14443a(ToSend, ToSendMax, timing);
	if(trigger)
		LED_A_ON();
  
	// Log reader command in trace buffer
	if (tracing) {
		LogTrace(frame, nbytes(bits), LastTimeProxToAirStart*16 + DELAY_ARM2AIR_AS_READER, (LastTimeProxToAirStart + LastProxToAirDuration)*16 + DELAY_ARM2AIR_AS_READER, par, TRUE);
	}
}

void ReaderTransmitPar(uint8_t* frame, uint16_t len, uint8_t *par, uint32_t *timing)
{
  ReaderTransmitBitsPar(frame, len*8, par, timing);
}

void ReaderTransmitBits(uint8_t* frame, uint16_t len, uint32_t *timing)
{
  // Generate parity and redirect
  uint8_t par[MAX_PARITY_SIZE];
  GetParity(frame, len/8, par);
  ReaderTransmitBitsPar(frame, len, par, timing);
}

void ReaderTransmit(uint8_t* frame, uint16_t len, uint32_t *timing)
{
  // Generate parity and redirect
  uint8_t par[MAX_PARITY_SIZE];
  GetParity(frame, len, par);
  ReaderTransmitBitsPar(frame, len*8, par, timing);
}

int ReaderReceiveOffset(uint8_t* receivedAnswer, uint16_t offset, uint8_t *parity)
{
	if (!GetIso14443aAnswerFromTag(receivedAnswer, parity, offset)) return FALSE;
	if (tracing) {
		LogTrace(receivedAnswer, Demod.len, Demod.startTime*16 - DELAY_AIR2ARM_AS_READER, Demod.endTime*16 - DELAY_AIR2ARM_AS_READER, parity, FALSE);
	}
	return Demod.len;
}

int ReaderReceive(uint8_t *receivedAnswer, uint8_t *parity)
{
	if (!GetIso14443aAnswerFromTag(receivedAnswer, parity, 0)) return FALSE;
	if (tracing) {
		LogTrace(receivedAnswer, Demod.len, Demod.startTime*16 - DELAY_AIR2ARM_AS_READER, Demod.endTime*16 - DELAY_AIR2ARM_AS_READER, parity, FALSE);
	}
	return Demod.len;
}

/* performs iso14443a anticollision procedure
 * fills the uid pointer unless NULL
 * fills resp_data unless NULL */
int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, uint32_t *cuid_ptr) {
	uint8_t wupa[]       = { 0x52 };  // 0x26 - REQA  0x52 - WAKE-UP
	uint8_t sel_all[]    = { 0x93,0x20 };
	uint8_t sel_uid[]    = { 0x93,0x70,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
	uint8_t rats[]       = { 0xE0,0x80,0x00,0x00 }; // FSD=256, FSDI=8, CID=0
	uint8_t resp[MAX_FRAME_SIZE]; // theoretically. A usual RATS will be much smaller
	uint8_t resp_par[MAX_PARITY_SIZE];
	byte_t uid_resp[4];
	size_t uid_resp_len;

	uint8_t sak = 0x04; // cascade uid
	int cascade_level = 0;
	int len;

	// Broadcast for a card, WUPA (0x52) will force response from all cards in the field
    ReaderTransmitBitsPar(wupa,7,0, NULL);
	
	// Receive the ATQA
	if(!ReaderReceive(resp, resp_par)) return 0;

	if(p_hi14a_card) {
		memcpy(p_hi14a_card->atqa, resp, 2);
		p_hi14a_card->uidlen = 0;
		memset(p_hi14a_card->uid,0,10);
	}

	// clear uid
	if (uid_ptr) {
		memset(uid_ptr,0,10);
	}

	// check for proprietary anticollision:
	if ((resp[0] & 0x1F) == 0) {
		return 3;
	}
	
	// OK we will select at least at cascade 1, lets see if first byte of UID was 0x88 in
	// which case we need to make a cascade 2 request and select - this is a long UID
	// While the UID is not complete, the 3nd bit (from the right) is set in the SAK.
	for(; sak & 0x04; cascade_level++) {
		// SELECT_* (L1: 0x93, L2: 0x95, L3: 0x97)
		sel_uid[0] = sel_all[0] = 0x93 + cascade_level * 2;

		// SELECT_ALL
		ReaderTransmit(sel_all, sizeof(sel_all), NULL);
		if (!ReaderReceive(resp, resp_par)) return 0;

		if (Demod.collisionPos) {			// we had a collision and need to construct the UID bit by bit
			memset(uid_resp, 0, 4);
			uint16_t uid_resp_bits = 0;
			uint16_t collision_answer_offset = 0;
			// anti-collision-loop:
			while (Demod.collisionPos) {
				Dbprintf("Multiple tags detected. Collision after Bit %d", Demod.collisionPos);
				for (uint16_t i = collision_answer_offset; i < Demod.collisionPos; i++, uid_resp_bits++) {	// add valid UID bits before collision point
					uint16_t UIDbit = (resp[i/8] >> (i % 8)) & 0x01;
					uid_resp[uid_resp_bits / 8] |= UIDbit << (uid_resp_bits % 8);
				}
				uid_resp[uid_resp_bits/8] |= 1 << (uid_resp_bits % 8);					// next time select the card(s) with a 1 in the collision position
				uid_resp_bits++;
				// construct anticollosion command:
				sel_uid[1] = ((2 + uid_resp_bits/8) << 4) | (uid_resp_bits & 0x07);  	// length of data in bytes and bits
				for (uint16_t i = 0; i <= uid_resp_bits/8; i++) {
					sel_uid[2+i] = uid_resp[i];
				}
				collision_answer_offset = uid_resp_bits%8;
				ReaderTransmitBits(sel_uid, 16 + uid_resp_bits, NULL);
				if (!ReaderReceiveOffset(resp, collision_answer_offset, resp_par)) return 0;
			}
			// finally, add the last bits and BCC of the UID
			for (uint16_t i = collision_answer_offset; i < (Demod.len-1)*8; i++, uid_resp_bits++) {
				uint16_t UIDbit = (resp[i/8] >> (i%8)) & 0x01;
				uid_resp[uid_resp_bits/8] |= UIDbit << (uid_resp_bits % 8);
			}

		} else {		// no collision, use the response to SELECT_ALL as current uid
			memcpy(uid_resp, resp, 4);
		}
		uid_resp_len = 4;

		// calculate crypto UID. Always use last 4 Bytes.
		if(cuid_ptr) {
			*cuid_ptr = bytes_to_num(uid_resp, 4);
		}

		// Construct SELECT UID command
		sel_uid[1] = 0x70;													// transmitting a full UID (1 Byte cmd, 1 Byte NVB, 4 Byte UID, 1 Byte BCC, 2 Bytes CRC)
		memcpy(sel_uid+2, uid_resp, 4);										// the UID
		sel_uid[6] = sel_uid[2] ^ sel_uid[3] ^ sel_uid[4] ^ sel_uid[5];  	// calculate and add BCC
		AppendCrc14443a(sel_uid, 7);										// calculate and add CRC
		ReaderTransmit(sel_uid, sizeof(sel_uid), NULL);

		// Receive the SAK
		if (!ReaderReceive(resp, resp_par)) return 0;
		sak = resp[0];

    // Test if more parts of the uid are coming
		if ((sak & 0x04) /* && uid_resp[0] == 0x88 */) {
			// Remove first byte, 0x88 is not an UID byte, it CT, see page 3 of:
			// http://www.nxp.com/documents/application_note/AN10927.pdf
			uid_resp[0] = uid_resp[1];
			uid_resp[1] = uid_resp[2];
			uid_resp[2] = uid_resp[3]; 

			uid_resp_len = 3;
		}

		if(uid_ptr) {
			memcpy(uid_ptr + (cascade_level*3), uid_resp, uid_resp_len);
		}

		if(p_hi14a_card) {
			memcpy(p_hi14a_card->uid + (cascade_level*3), uid_resp, uid_resp_len);
			p_hi14a_card->uidlen += uid_resp_len;
		}
	}

	if(p_hi14a_card) {
		p_hi14a_card->sak = sak;
		p_hi14a_card->ats_len = 0;
	}

	// non iso14443a compliant tag
	if( (sak & 0x20) == 0) return 2; 

	// Request for answer to select
	AppendCrc14443a(rats, 2);
	ReaderTransmit(rats, sizeof(rats), NULL);

	if (!(len = ReaderReceive(resp, resp_par))) return 0;

	
	if(p_hi14a_card) {
		memcpy(p_hi14a_card->ats, resp, sizeof(p_hi14a_card->ats));
		p_hi14a_card->ats_len = len;
	}

	// reset the PCB block number
	iso14_pcb_blocknum = 0;

	// set default timeout based on ATS
	iso14a_set_ATS_timeout(resp);

	return 1;	
}

void iso14443a_setup(uint8_t fpga_minor_mode) {
	FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
	// Set up the synchronous serial port
	FpgaSetupSsc();
	// connect Demodulated Signal to ADC:
	SetAdcMuxFor(GPIO_MUXSEL_HIPKD);

	// Signal field is on with the appropriate LED
	if (fpga_minor_mode == FPGA_HF_ISO14443A_READER_MOD
		|| fpga_minor_mode == FPGA_HF_ISO14443A_READER_LISTEN) {
		LED_D_ON();
	} else {
		LED_D_OFF();
	}
	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | fpga_minor_mode);

	// Start the timer
	StartCountSspClk();
	
	DemodReset();
	UartReset();
	NextTransferTime = 2*DELAY_ARM2AIR_AS_READER;
	iso14a_set_timeout(10*106); // 10ms default
}

int iso14_apdu(uint8_t *cmd, uint16_t cmd_len, void *data) {
	uint8_t parity[MAX_PARITY_SIZE];
	uint8_t real_cmd[cmd_len+4];
	real_cmd[0] = 0x0a; //I-Block
	// put block number into the PCB
	real_cmd[0] |= iso14_pcb_blocknum;
	real_cmd[1] = 0x00; //CID: 0 //FIXME: allow multiple selected cards
	memcpy(real_cmd+2, cmd, cmd_len);
	AppendCrc14443a(real_cmd,cmd_len+2);
 
	ReaderTransmit(real_cmd, cmd_len+4, NULL);
	size_t len = ReaderReceive(data, parity);
	uint8_t *data_bytes = (uint8_t *) data;
	if (!len)
		return 0; //DATA LINK ERROR
	// if we received an I- or R(ACK)-Block with a block number equal to the
	// current block number, toggle the current block number
	else if (len >= 4 // PCB+CID+CRC = 4 bytes
	         && ((data_bytes[0] & 0xC0) == 0 // I-Block
	             || (data_bytes[0] & 0xD0) == 0x80) // R-Block with ACK bit set to 0
	         && (data_bytes[0] & 0x01) == iso14_pcb_blocknum) // equal block numbers
	{
		iso14_pcb_blocknum ^= 1;
	}

	return len;
}

//-----------------------------------------------------------------------------
// Read an ISO 14443a tag. Send out commands and store answers.
//
//-----------------------------------------------------------------------------
void ReaderIso14443a(UsbCommand *c)
{
	iso14a_command_t param = c->arg[0];
	uint8_t *cmd = c->d.asBytes;
	size_t len = c->arg[1] & 0xffff;
	size_t lenbits = c->arg[1] >> 16;
	uint32_t timeout = c->arg[2];
	uint32_t arg0 = 0;
	byte_t buf[USB_CMD_DATA_SIZE];
	uint8_t par[MAX_PARITY_SIZE];
  
	if(param & ISO14A_CONNECT) {
		clear_trace();
	}

	set_tracing(TRUE);

	if(param & ISO14A_REQUEST_TRIGGER) {
		iso14a_set_trigger(TRUE);
	}

	if(param & ISO14A_CONNECT) {
		iso14443a_setup(FPGA_HF_ISO14443A_READER_LISTEN);
		if(!(param & ISO14A_NO_SELECT)) {
			iso14a_card_select_t *card = (iso14a_card_select_t*)buf;
			arg0 = iso14443a_select_card(NULL,card,NULL);
			cmd_send(CMD_ACK,arg0,card->uidlen,0,buf,sizeof(iso14a_card_select_t));
		}
	}

	if(param & ISO14A_SET_TIMEOUT) {
		iso14a_set_timeout(timeout);
	}

	if(param & ISO14A_APDU) {
		arg0 = iso14_apdu(cmd, len, buf);
		cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
	}

	if(param & ISO14A_RAW) {
		if(param & ISO14A_APPEND_CRC) {
			if(param & ISO14A_TOPAZMODE) {
				AppendCrc14443b(cmd,len);
			} else {
				AppendCrc14443a(cmd,len);
			}
			len += 2;
			if (lenbits) lenbits += 16;
		}
		if(lenbits>0) {				// want to send a specific number of bits (e.g. short commands)
			if(param & ISO14A_TOPAZMODE) {
				int bits_to_send = lenbits;
				uint16_t i = 0;
				ReaderTransmitBitsPar(&cmd[i++], MIN(bits_to_send, 7), NULL, NULL);		// first byte is always short (7bits) and no parity
				bits_to_send -= 7;
				while (bits_to_send > 0) {
					ReaderTransmitBitsPar(&cmd[i++], MIN(bits_to_send, 8), NULL, NULL);	// following bytes are 8 bit and no parity
					bits_to_send -= 8;
				}
			} else {
			GetParity(cmd, lenbits/8, par);
				ReaderTransmitBitsPar(cmd, lenbits, par, NULL);							// bytes are 8 bit with odd parity
			}
		} else {					// want to send complete bytes only
			if(param & ISO14A_TOPAZMODE) {
				uint16_t i = 0;
				ReaderTransmitBitsPar(&cmd[i++], 7, NULL, NULL);						// first byte: 7 bits, no paritiy
				while (i < len) {
					ReaderTransmitBitsPar(&cmd[i++], 8, NULL, NULL);					// following bytes: 8 bits, no paritiy
				}
		} else {
				ReaderTransmit(cmd,len, NULL);											// 8 bits, odd parity
			}
		}
		arg0 = ReaderReceive(buf, par);
		cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
	}

	if(param & ISO14A_REQUEST_TRIGGER) {
		iso14a_set_trigger(FALSE);
	}

	if(param & ISO14A_NO_DISCONNECT) {
		return;
	}

	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	set_tracing(FALSE);
	LEDsoff();
}


// Determine the distance between two nonces.
// Assume that the difference is small, but we don't know which is first.
// Therefore try in alternating directions.
int32_t dist_nt(uint32_t nt1, uint32_t nt2) {

	uint16_t i;
	uint32_t nttmp1, nttmp2;

	if (nt1 == nt2) return 0;

	nttmp1 = nt1;
	nttmp2 = nt2;
	
	for (i = 1; i < 0xFFFF; i++) {
		nttmp1 = prng_successor(nttmp1, 1);
		if (nttmp1 == nt2) return i;
		nttmp2 = prng_successor(nttmp2, 1);
			if (nttmp2 == nt1) return -i;
		}
	
	return(-99999); // either nt1 or nt2 are invalid nonces
}


//-----------------------------------------------------------------------------
// Recover several bits of the cypher stream. This implements (first stages of)
// the algorithm described in "The Dark Side of Security by Obscurity and
// Cloning MiFare Classic Rail and Building Passes, Anywhere, Anytime"
// (article by Nicolas T. Courtois, 2009)
//-----------------------------------------------------------------------------
void ReaderMifare(bool first_try)
{
	// Mifare AUTH
	uint8_t mf_auth[]    = { 0x60,0x00,0xf5,0x7b };
	uint8_t mf_nr_ar[]   = { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 };
	static uint8_t mf_nr_ar3;

	uint8_t receivedAnswer[MAX_MIFARE_FRAME_SIZE];
	uint8_t receivedAnswerPar[MAX_MIFARE_PARITY_SIZE];

	if (first_try) { 
		iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
	}
	
	// free eventually allocated BigBuf memory. We want all for tracing.
	BigBuf_free();
	
	clear_trace();
	set_tracing(TRUE);

	byte_t nt_diff = 0;
	uint8_t par[1] = {0};	// maximum 8 Bytes to be sent here, 1 byte parity is therefore enough
	static byte_t par_low = 0;
	bool led_on = TRUE;
	uint8_t uid[10]  ={0};
	uint32_t cuid;

	uint32_t nt = 0;
	uint32_t previous_nt = 0;
	static uint32_t nt_attacked = 0;
	byte_t par_list[8] = {0x00};
	byte_t ks_list[8] = {0x00};

   #define PRNG_SEQUENCE_LENGTH  (1 << 16);
	static uint32_t sync_time = 0;
	static int32_t sync_cycles = 0;
	int catch_up_cycles = 0;
	int last_catch_up = 0;
	uint16_t elapsed_prng_sequences;
	uint16_t consecutive_resyncs = 0;
	int isOK = 0;

	if (first_try) { 
		mf_nr_ar3 = 0;
		sync_time = GetCountSspClk() & 0xfffffff8;
		sync_cycles = PRNG_SEQUENCE_LENGTH; //65536;	//0x10000			// theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the nonces).
		nt_attacked = 0;
		par[0] = 0;
	}
	else {
		// we were unsuccessful on a previous call. Try another READER nonce (first 3 parity bits remain the same)
		mf_nr_ar3++;
		mf_nr_ar[3] = mf_nr_ar3;
		par[0] = par_low;
	}

	LED_A_ON();
	LED_B_OFF();
	LED_C_OFF();
	

	#define MAX_UNEXPECTED_RANDOM	4		// maximum number of unexpected (i.e. real) random numbers when trying to sync. Then give up.
	#define MAX_SYNC_TRIES			32
	#define NUM_DEBUG_INFOS			8		// per strategy
	#define MAX_STRATEGY			3
	uint16_t unexpected_random = 0;
	uint16_t sync_tries = 0;
	int16_t debug_info_nr = -1;
	uint16_t strategy = 0;
	int32_t debug_info[MAX_STRATEGY][NUM_DEBUG_INFOS];
	uint32_t select_time;
	uint32_t halt_time;
  
	for(uint16_t i = 0; TRUE; i++) {
		
		LED_C_ON();
		WDT_HIT();

		// Test if the action was cancelled
		if(BUTTON_PRESS()) {
			isOK = -1;
			break;
		}
		
		if (strategy == 2) {
			// test with additional hlt command
			halt_time = 0;
			int len = mifare_sendcmd_short(NULL, false, 0x50, 0x00, receivedAnswer, receivedAnswerPar, &halt_time);
			if (len && MF_DBGLEVEL >= 3) {
				Dbprintf("Unexpected response of %d bytes to hlt command (additional debugging).", len);
			}
		}

		if (strategy == 3) {
			// test with FPGA power off/on
			FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
			SpinDelay(200);
			iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
			SpinDelay(100);
		}
		
		if(!iso14443a_select_card(uid, NULL, &cuid)) {
			if (MF_DBGLEVEL >= 1)	Dbprintf("Mifare: Can't select card");
			continue;
		}
		select_time = GetCountSspClk();

		elapsed_prng_sequences = 1;
		if (debug_info_nr == -1) {
			sync_time = (sync_time & 0xfffffff8) + sync_cycles + catch_up_cycles;
			catch_up_cycles = 0;

			// if we missed the sync time already, advance to the next nonce repeat
			while(GetCountSspClk() > sync_time) {
				elapsed_prng_sequences++;
				sync_time = (sync_time & 0xfffffff8) + sync_cycles;
			}

			// Transmit MIFARE_CLASSIC_AUTH at synctime. Should result in returning the same tag nonce (== nt_attacked) 
			ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
		} else {
			// collect some information on tag nonces for debugging:
			#define DEBUG_FIXED_SYNC_CYCLES	PRNG_SEQUENCE_LENGTH
			if (strategy == 0) {
				// nonce distances at fixed time after card select:
				sync_time = select_time + DEBUG_FIXED_SYNC_CYCLES;
			} else if (strategy == 1) {
				// nonce distances at fixed time between authentications:
				sync_time = sync_time + DEBUG_FIXED_SYNC_CYCLES;
			} else if (strategy == 2) {
				// nonce distances at fixed time after halt:
				sync_time = halt_time + DEBUG_FIXED_SYNC_CYCLES;
			} else {
				// nonce_distances at fixed time after power on
				sync_time = DEBUG_FIXED_SYNC_CYCLES;
			}
			ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
		}			

		// Receive the (4 Byte) "random" nonce
		if (!ReaderReceive(receivedAnswer, receivedAnswerPar)) {
			if (MF_DBGLEVEL >= 1)	Dbprintf("Mifare: Couldn't receive tag nonce");
			continue;
		  }

		previous_nt = nt;
		nt = bytes_to_num(receivedAnswer, 4);

		// Transmit reader nonce with fake par
		ReaderTransmitPar(mf_nr_ar, sizeof(mf_nr_ar), par, NULL);

		if (first_try && previous_nt && !nt_attacked) { // we didn't calibrate our clock yet
			int nt_distance = dist_nt(previous_nt, nt);
			if (nt_distance == 0) {
				nt_attacked = nt;
			} else {
				if (nt_distance == -99999) { // invalid nonce received
					unexpected_random++;
					if (unexpected_random > MAX_UNEXPECTED_RANDOM) {
						isOK = -3;		// Card has an unpredictable PRNG. Give up	
						break;
					} else {
						continue;		// continue trying...
					}
				}
				if (++sync_tries > MAX_SYNC_TRIES) {
					if (strategy > MAX_STRATEGY || MF_DBGLEVEL < 3) {
						isOK = -4; 			// Card's PRNG runs at an unexpected frequency or resets unexpectedly
						break;
					} else {				// continue for a while, just to collect some debug info
						debug_info[strategy][debug_info_nr] = nt_distance;
						debug_info_nr++;
						if (debug_info_nr == NUM_DEBUG_INFOS) {
							strategy++;
							debug_info_nr = 0;
						}
						continue;
					}
				}
				sync_cycles = (sync_cycles - nt_distance/elapsed_prng_sequences);
				if (sync_cycles <= 0) {
					sync_cycles += PRNG_SEQUENCE_LENGTH;
				}
				if (MF_DBGLEVEL >= 3) {
					Dbprintf("calibrating in cycle %d. nt_distance=%d, elapsed_prng_sequences=%d, new sync_cycles: %d\n", i, nt_distance, elapsed_prng_sequences, sync_cycles);
				}
				continue;
			}
		}

		if ((nt != nt_attacked) && nt_attacked) { 	// we somehow lost sync. Try to catch up again...
			catch_up_cycles = -dist_nt(nt_attacked, nt);
			if (catch_up_cycles == 99999) {			// invalid nonce received. Don't resync on that one.
				catch_up_cycles = 0;
				continue;
			}
			catch_up_cycles /= elapsed_prng_sequences;
			if (catch_up_cycles == last_catch_up) {
				consecutive_resyncs++;
			}
			else {
				last_catch_up = catch_up_cycles;
			    consecutive_resyncs = 0;
			}
			if (consecutive_resyncs < 3) {
				if (MF_DBGLEVEL >= 3) Dbprintf("Lost sync in cycle %d. nt_distance=%d. Consecutive Resyncs = %d. Trying one time catch up...\n", i, -catch_up_cycles, consecutive_resyncs);
			}
			else {	
				sync_cycles = sync_cycles + catch_up_cycles;
				if (MF_DBGLEVEL >= 3) Dbprintf("Lost sync in cycle %d for the fourth time consecutively (nt_distance = %d). Adjusting sync_cycles to %d.\n", i, -catch_up_cycles, sync_cycles);
				last_catch_up = 0;
				catch_up_cycles = 0;
				consecutive_resyncs = 0;
			}
			continue;
		}
 
		consecutive_resyncs = 0;
		
		// Receive answer. This will be a 4 Bit NACK when the 8 parity bits are OK after decoding
		if (ReaderReceive(receivedAnswer, receivedAnswerPar)) {
			catch_up_cycles = 8; 	// the PRNG is delayed by 8 cycles due to the NAC (4Bits = 0x05 encrypted) transfer
	
			if (nt_diff == 0) {
				par_low = par[0] & 0xE0; // there is no need to check all parities for other nt_diff. Parity Bits for mf_nr_ar[0..2] won't change
			}

			led_on = !led_on;
			if(led_on) LED_B_ON(); else LED_B_OFF();

			par_list[nt_diff] = SwapBits(par[0], 8);
			ks_list[nt_diff] = receivedAnswer[0] ^ 0x05;

			// Test if the information is complete
			if (nt_diff == 0x07) {
				isOK = 1;
				break;
			}

			nt_diff = (nt_diff + 1) & 0x07;
			mf_nr_ar[3] = (mf_nr_ar[3] & 0x1F) | (nt_diff << 5);
			par[0] = par_low;
		} else {
			if (nt_diff == 0 && first_try)
			{
				par[0]++;
				if (par[0] == 0x00) {		// tried all 256 possible parities without success. Card doesn't send NACK.
					isOK = -2;
					break;
				}
			} else {
				par[0] = ((par[0] & 0x1F) + 1) | par_low;
			}
		}
	}


	mf_nr_ar[3] &= 0x1F;
	
	if (isOK == -4) {
		if (MF_DBGLEVEL >= 3) {
			for (uint16_t i = 0; i <= MAX_STRATEGY; i++) {
				for(uint16_t j = 0; j < NUM_DEBUG_INFOS; j++) {
					Dbprintf("collected debug info[%d][%d] = %d", i, j, debug_info[i][j]);
				}
			}
		}
	}
	
	byte_t buf[28];
	memcpy(buf + 0,  uid, 4);
	num_to_bytes(nt, 4, buf + 4);
	memcpy(buf + 8,  par_list, 8);
	memcpy(buf + 16, ks_list, 8);
	memcpy(buf + 24, mf_nr_ar, 4);
		
	cmd_send(CMD_ACK,isOK,0,0,buf,28);

	// Thats it...
	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	LEDsoff();

	set_tracing(FALSE);
}

/**
  *MIFARE 1K simulate.
  *
  *@param flags :
  *	FLAG_INTERACTIVE - In interactive mode, we are expected to finish the operation with an ACK
  * 4B_FLAG_UID_IN_DATA - means that there is a 4-byte UID in the data-section, we're expected to use that
  * 7B_FLAG_UID_IN_DATA - means that there is a 7-byte UID in the data-section, we're expected to use that
  *	FLAG_NR_AR_ATTACK  - means we should collect NR_AR responses for bruteforcing later
  *@param exitAfterNReads, exit simulation after n blocks have been read, 0 is inifite
  */
void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *datain)
{
	int cardSTATE = MFEMUL_NOFIELD;
	int _7BUID = 0;
	int vHf = 0;	// in mV
	int res;
	uint32_t selTimer = 0;
	uint32_t authTimer = 0;
	uint16_t len = 0;
	uint8_t cardWRBL = 0;
	uint8_t cardAUTHSC = 0;
	uint8_t cardAUTHKEY = 0xff;  // no authentication
//	uint32_t cardRr = 0;
	uint32_t cuid = 0;
	//uint32_t rn_enc = 0;
	uint32_t ans = 0;
	uint32_t cardINTREG = 0;
	uint8_t cardINTBLOCK = 0;
	struct Crypto1State mpcs = {0, 0};
	struct Crypto1State *pcs;
	pcs = &mpcs;
	uint32_t numReads = 0;//Counts numer of times reader read a block
	uint8_t receivedCmd[MAX_MIFARE_FRAME_SIZE];
	uint8_t receivedCmd_par[MAX_MIFARE_PARITY_SIZE];
	uint8_t response[MAX_MIFARE_FRAME_SIZE];
	uint8_t response_par[MAX_MIFARE_PARITY_SIZE];
	
	uint8_t rATQA[] = {0x04, 0x00}; // Mifare classic 1k 4BUID
	uint8_t rUIDBCC1[] = {0xde, 0xad, 0xbe, 0xaf, 0x62};
	uint8_t rUIDBCC2[] = {0xde, 0xad, 0xbe, 0xaf, 0x62}; // !!!
	//uint8_t rSAK[] = {0x08, 0xb6, 0xdd}; // Mifare Classic
	uint8_t rSAK[] = {0x09, 0x3f, 0xcc };  // Mifare Mini 
	uint8_t rSAK1[] = {0x04, 0xda, 0x17};

	uint8_t rAUTH_NT[] = {0x01, 0x01, 0x01, 0x01};
	uint8_t rAUTH_AT[] = {0x00, 0x00, 0x00, 0x00};
		
	//Here, we collect UID,NT,AR,NR,UID2,NT2,AR2,NR2
	// This can be used in a reader-only attack.
	// (it can also be retrieved via 'hf 14a list', but hey...
	uint32_t ar_nr_responses[] = {0,0,0,0,0,0,0,0,0,0};
	uint8_t ar_nr_collected = 0;

	// Authenticate response - nonce
	uint32_t nonce = bytes_to_num(rAUTH_NT, 4);
	
	//-- Determine the UID
	// Can be set from emulator memory, incoming data
	// and can be 7 or 4 bytes long
	if (flags & FLAG_4B_UID_IN_DATA)
	{
		// 4B uid comes from data-portion of packet
		memcpy(rUIDBCC1,datain,4);
		rUIDBCC1[4] = rUIDBCC1[0] ^ rUIDBCC1[1] ^ rUIDBCC1[2] ^ rUIDBCC1[3];

	} else if (flags & FLAG_7B_UID_IN_DATA) {
		// 7B uid comes from data-portion of packet
		memcpy(&rUIDBCC1[1],datain,3);
		memcpy(rUIDBCC2, datain+3, 4);
		_7BUID = true;
	} else {
		// get UID from emul memory
		emlGetMemBt(receivedCmd, 7, 1);
		_7BUID = !(receivedCmd[0] == 0x00);
		if (!_7BUID) {                     // ---------- 4BUID
			emlGetMemBt(rUIDBCC1, 0, 4);
		} else {                           // ---------- 7BUID
			emlGetMemBt(&rUIDBCC1[1], 0, 3);
			emlGetMemBt(rUIDBCC2, 3, 4);
		}
	}

	// save uid.
	ar_nr_responses[0*5]   = bytes_to_num(rUIDBCC1+1, 3);
	if ( _7BUID )
		ar_nr_responses[0*5+1] = bytes_to_num(rUIDBCC2, 4);

	/*
	 * Regardless of what method was used to set the UID, set fifth byte and modify
	 * the ATQA for 4 or 7-byte UID
	 */
	rUIDBCC1[4] = rUIDBCC1[0] ^ rUIDBCC1[1] ^ rUIDBCC1[2] ^ rUIDBCC1[3];
	if (_7BUID) {
		rATQA[0] = 0x44;
		rUIDBCC1[0] = 0x88;
		rUIDBCC1[4] = rUIDBCC1[0] ^ rUIDBCC1[1] ^ rUIDBCC1[2] ^ rUIDBCC1[3];
		rUIDBCC2[4] = rUIDBCC2[0] ^ rUIDBCC2[1] ^ rUIDBCC2[2] ^ rUIDBCC2[3];
	}

	if (MF_DBGLEVEL >= 1)	{
		if (!_7BUID) {
			Dbprintf("4B UID: %02x%02x%02x%02x", 
				rUIDBCC1[0], rUIDBCC1[1], rUIDBCC1[2], rUIDBCC1[3]);
		} else {
			Dbprintf("7B UID: (%02x)%02x%02x%02x%02x%02x%02x%02x",
				rUIDBCC1[0], rUIDBCC1[1], rUIDBCC1[2], rUIDBCC1[3],
				rUIDBCC2[0], rUIDBCC2[1] ,rUIDBCC2[2], rUIDBCC2[3]);
		}
	}

	// We need to listen to the high-frequency, peak-detected path.
	iso14443a_setup(FPGA_HF_ISO14443A_TAGSIM_LISTEN);

	// free eventually allocated BigBuf memory but keep Emulator Memory
	BigBuf_free_keep_EM();

	// clear trace
	clear_trace();
	set_tracing(TRUE);


	bool finished = FALSE;
	while (!BUTTON_PRESS() && !finished) {
		WDT_HIT();

		// find reader field
		if (cardSTATE == MFEMUL_NOFIELD) {
			vHf = (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
			if (vHf > MF_MINFIELDV) {
				cardSTATE_TO_IDLE();
				LED_A_ON();
			}
		} 
		if(cardSTATE == MFEMUL_NOFIELD) continue;

		//Now, get data
		res = EmGetCmd(receivedCmd, &len, receivedCmd_par);
		if (res == 2) { //Field is off!
			cardSTATE = MFEMUL_NOFIELD;
			LEDsoff();
			continue;
		} else if (res == 1) {
			break; 	//return value 1 means button press
		}
			
		// REQ or WUP request in ANY state and WUP in HALTED state
		if (len == 1 && ((receivedCmd[0] == 0x26 && cardSTATE != MFEMUL_HALTED) || receivedCmd[0] == 0x52)) {
			selTimer = GetTickCount();
			EmSendCmdEx(rATQA, sizeof(rATQA), (receivedCmd[0] == 0x52));
			cardSTATE = MFEMUL_SELECT1;

			// init crypto block
			LED_B_OFF();
			LED_C_OFF();
			crypto1_destroy(pcs);
			cardAUTHKEY = 0xff;
			continue;
		}
		
		switch (cardSTATE) {
			case MFEMUL_NOFIELD:
			case MFEMUL_HALTED:
			case MFEMUL_IDLE:{
				LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
				break;
			}
			case MFEMUL_SELECT1:{
				// select all
				if (len == 2 && (receivedCmd[0] == 0x93 && receivedCmd[1] == 0x20)) {
					if (MF_DBGLEVEL >= 4)	Dbprintf("SELECT ALL received");
					EmSendCmd(rUIDBCC1, sizeof(rUIDBCC1));
					break;
				}

				if (MF_DBGLEVEL >= 4 && len == 9 && receivedCmd[0] == 0x93 && receivedCmd[1] == 0x70 )
				{
					Dbprintf("SELECT %02x%02x%02x%02x received",receivedCmd[2],receivedCmd[3],receivedCmd[4],receivedCmd[5]);
				}
				// select card
				if (len == 9 && 
						(receivedCmd[0] == 0x93 && receivedCmd[1] == 0x70 && memcmp(&receivedCmd[2], rUIDBCC1, 4) == 0)) {
					EmSendCmd(_7BUID?rSAK1:rSAK, _7BUID?sizeof(rSAK1):sizeof(rSAK));
					cuid = bytes_to_num(rUIDBCC1, 4);
					if (!_7BUID) {
						cardSTATE = MFEMUL_WORK;
						LED_B_ON();
						if (MF_DBGLEVEL >= 4)	Dbprintf("--> WORK. anticol1 time: %d", GetTickCount() - selTimer);
						break;
					} else {
						cardSTATE = MFEMUL_SELECT2;
					}
				}
				break;
			}
			case MFEMUL_AUTH1:{
				if( len != 8)
				{
					cardSTATE_TO_IDLE();
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					break;
				}

				uint32_t ar = bytes_to_num(receivedCmd, 4);
				uint32_t nr = bytes_to_num(&receivedCmd[4], 4);

				//Collect AR/NR
				//if(ar_nr_collected < 2 && cardAUTHSC == 2){
				if(ar_nr_collected < 2){
					if(ar_nr_responses[2] != ar)
					{// Avoid duplicates... probably not necessary, ar should vary. 
						//ar_nr_responses[ar_nr_collected*5]   = 0;
						//ar_nr_responses[ar_nr_collected*5+1] = 0;
						ar_nr_responses[ar_nr_collected*5+2] = nonce;
						ar_nr_responses[ar_nr_collected*5+3] = nr;
						ar_nr_responses[ar_nr_collected*5+4] = ar;
						ar_nr_collected++;
					}						
					// Interactive mode flag, means we need to send ACK
					if(flags & FLAG_INTERACTIVE && ar_nr_collected == 2)
					{
						finished = true;
					}
				}

				// --- crypto
				//crypto1_word(pcs, ar , 1);
				//cardRr = nr ^ crypto1_word(pcs, 0, 0);

				//test if auth OK
				//if (cardRr != prng_successor(nonce, 64)){
					
					//if (MF_DBGLEVEL >= 4) Dbprintf("AUTH FAILED for sector %d with key %c. cardRr=%08x, succ=%08x",
					//	cardAUTHSC, cardAUTHKEY == 0 ? 'A' : 'B',
					//		cardRr, prng_successor(nonce, 64));
					// Shouldn't we respond anything here?
					// Right now, we don't nack or anything, which causes the
					// reader to do a WUPA after a while. /Martin
					// -- which is the correct response. /piwi
					//cardSTATE_TO_IDLE();
					//LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					//break;
				//}

				ans = prng_successor(nonce, 96) ^ crypto1_word(pcs, 0, 0);

				num_to_bytes(ans, 4, rAUTH_AT);
				// --- crypto
				EmSendCmd(rAUTH_AT, sizeof(rAUTH_AT));
				LED_C_ON();
				cardSTATE = MFEMUL_WORK;
				if (MF_DBGLEVEL >= 4)	Dbprintf("AUTH COMPLETED for sector %d with key %c. time=%d", 
					cardAUTHSC, cardAUTHKEY == 0 ? 'A' : 'B',
					GetTickCount() - authTimer);
				break;
			}
			case MFEMUL_SELECT2:{
				if (!len) { 
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					break;
				}
				if (len == 2 && (receivedCmd[0] == 0x95 && receivedCmd[1] == 0x20)) {
					EmSendCmd(rUIDBCC2, sizeof(rUIDBCC2));
					break;
				}

				// select 2 card
				if (len == 9 && 
						(receivedCmd[0] == 0x95 && receivedCmd[1] == 0x70 && memcmp(&receivedCmd[2], rUIDBCC2, 4) == 0)) {
					EmSendCmd(rSAK, sizeof(rSAK));
					cuid = bytes_to_num(rUIDBCC2, 4);
					cardSTATE = MFEMUL_WORK;
					LED_B_ON();
					if (MF_DBGLEVEL >= 4)	Dbprintf("--> WORK. anticol2 time: %d", GetTickCount() - selTimer);
					break;
				}
				
				// i guess there is a command). go into the work state.
				if (len != 4) {
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					break;
				}
				cardSTATE = MFEMUL_WORK;
				//goto lbWORK;
				//intentional fall-through to the next case-stmt
			}

			case MFEMUL_WORK:{
				if (len == 0) {
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					break;
				}
				
				bool encrypted_data = (cardAUTHKEY != 0xFF) ;

				if(encrypted_data) {
					// decrypt seqence
					mf_crypto1_decrypt(pcs, receivedCmd, len);
				}
				
				if (len == 4 && (receivedCmd[0] == 0x60 || receivedCmd[0] == 0x61)) {
					authTimer = GetTickCount();
					cardAUTHSC = receivedCmd[1] / 4;  // received block num
					cardAUTHKEY = receivedCmd[0] - 0x60;
					crypto1_destroy(pcs);//Added by martin
					crypto1_create(pcs, emlGetKey(cardAUTHSC, cardAUTHKEY));

					if (!encrypted_data) { // first authentication
						if (MF_DBGLEVEL >= 4) Dbprintf("Reader authenticating for block %d (0x%02x) with key %d",receivedCmd[1] ,receivedCmd[1],cardAUTHKEY  );

						crypto1_word(pcs, cuid ^ nonce, 0);//Update crypto state
						num_to_bytes(nonce, 4, rAUTH_AT); // Send nonce
					} else { // nested authentication
						if (MF_DBGLEVEL >= 4) Dbprintf("Reader doing nested authentication for block %d (0x%02x) with key %d",receivedCmd[1] ,receivedCmd[1],cardAUTHKEY );
						ans = nonce ^ crypto1_word(pcs, cuid ^ nonce, 0); 
						num_to_bytes(ans, 4, rAUTH_AT);
					}

					EmSendCmd(rAUTH_AT, sizeof(rAUTH_AT));
					//Dbprintf("Sending rAUTH %02x%02x%02x%02x", rAUTH_AT[0],rAUTH_AT[1],rAUTH_AT[2],rAUTH_AT[3]);
					cardSTATE = MFEMUL_AUTH1;
					break;
				}
				
				// rule 13 of 7.5.3. in ISO 14443-4. chaining shall be continued
				// BUT... ACK --> NACK
				if (len == 1 && receivedCmd[0] == CARD_ACK) {
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
					break;
				}
				
				// rule 12 of 7.5.3. in ISO 14443-4. R(NAK) --> R(ACK)
				if (len == 1 && receivedCmd[0] == CARD_NACK_NA) {
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_ACK));
					break;
				}
				
				if(len != 4) {
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					break;
				}

				if(receivedCmd[0] == 0x30 // read block
						|| receivedCmd[0] == 0xA0 // write block
						|| receivedCmd[0] == 0xC0 // inc
						|| receivedCmd[0] == 0xC1 // dec
						|| receivedCmd[0] == 0xC2 // restore
						|| receivedCmd[0] == 0xB0) { // transfer
					if (receivedCmd[1] >= 16 * 4) {
						EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
						if (MF_DBGLEVEL >= 4) Dbprintf("Reader tried to operate (0x%02) on out of range block: %d (0x%02x), nacking",receivedCmd[0],receivedCmd[1],receivedCmd[1]);
						break;
					}

					if (receivedCmd[1] / 4 != cardAUTHSC) {
						EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
						if (MF_DBGLEVEL >= 4) Dbprintf("Reader tried to operate (0x%02) on block (0x%02x) not authenticated for (0x%02x), nacking",receivedCmd[0],receivedCmd[1],cardAUTHSC);
						break;
					}
				}
				// read block
				if (receivedCmd[0] == 0x30) {
					if (MF_DBGLEVEL >= 4) {
						Dbprintf("Reader reading block %d (0x%02x)",receivedCmd[1],receivedCmd[1]);
					}
					emlGetMem(response, receivedCmd[1], 1);
					AppendCrc14443a(response, 16);
					mf_crypto1_encrypt(pcs, response, 18, response_par);
					EmSendCmdPar(response, 18, response_par);
					numReads++;
					if(exitAfterNReads > 0 && numReads >= exitAfterNReads) {
						Dbprintf("%d reads done, exiting", numReads);
						finished = true;
					}
					break;
				}
				// write block
				if (receivedCmd[0] == 0xA0) {
					if (MF_DBGLEVEL >= 4) Dbprintf("RECV 0xA0 write block %d (%02x)",receivedCmd[1],receivedCmd[1]);
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_ACK));
					cardSTATE = MFEMUL_WRITEBL2;
					cardWRBL = receivedCmd[1];
					break;
				}
				// increment, decrement, restore
				if (receivedCmd[0] == 0xC0 || receivedCmd[0] == 0xC1 || receivedCmd[0] == 0xC2) {
					if (MF_DBGLEVEL >= 4) Dbprintf("RECV 0x%02x inc(0xC1)/dec(0xC0)/restore(0xC2) block %d (%02x)",receivedCmd[0],receivedCmd[1],receivedCmd[1]);
					if (emlCheckValBl(receivedCmd[1])) {
						if (MF_DBGLEVEL >= 4) Dbprintf("Reader tried to operate on block, but emlCheckValBl failed, nacking");
						EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
						break;
					}
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_ACK));
					if (receivedCmd[0] == 0xC1)
						cardSTATE = MFEMUL_INTREG_INC;
					if (receivedCmd[0] == 0xC0)
						cardSTATE = MFEMUL_INTREG_DEC;
					if (receivedCmd[0] == 0xC2)
						cardSTATE = MFEMUL_INTREG_REST;
					cardWRBL = receivedCmd[1];
					break;
				}
				// transfer
				if (receivedCmd[0] == 0xB0) {
					if (MF_DBGLEVEL >= 4) Dbprintf("RECV 0x%02x transfer block %d (%02x)",receivedCmd[0],receivedCmd[1],receivedCmd[1]);
					if (emlSetValBl(cardINTREG, cardINTBLOCK, receivedCmd[1]))
						EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
					else
						EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_ACK));
					break;
				}
				// halt
				if (receivedCmd[0] == 0x50 && receivedCmd[1] == 0x00) {
					LED_B_OFF();
					LED_C_OFF();
					cardSTATE = MFEMUL_HALTED;
					if (MF_DBGLEVEL >= 4)	Dbprintf("--> HALTED. Selected time: %d ms",  GetTickCount() - selTimer);
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
					break;
				}
				// RATS
				if (receivedCmd[0] == 0xe0) {//RATS
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
					break;
				}
				// command not allowed
				if (MF_DBGLEVEL >= 4)	Dbprintf("Received command not allowed, nacking");
				EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
				break;
			}
			case MFEMUL_WRITEBL2:{
				if (len == 18){
					mf_crypto1_decrypt(pcs, receivedCmd, len);
					emlSetMem(receivedCmd, cardWRBL, 1);
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_ACK));
					cardSTATE = MFEMUL_WORK;
				} else {
					cardSTATE_TO_IDLE();
					LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
				}
				break;
			}
			
			case MFEMUL_INTREG_INC:{
				mf_crypto1_decrypt(pcs, receivedCmd, len);
				memcpy(&ans, receivedCmd, 4);
				if (emlGetValBl(&cardINTREG, &cardINTBLOCK, cardWRBL)) {
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
					cardSTATE_TO_IDLE();
					break;
				} 
				LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
				cardINTREG = cardINTREG + ans;
				cardSTATE = MFEMUL_WORK;
				break;
			}
			case MFEMUL_INTREG_DEC:{
				mf_crypto1_decrypt(pcs, receivedCmd, len);
				memcpy(&ans, receivedCmd, 4);
				if (emlGetValBl(&cardINTREG, &cardINTBLOCK, cardWRBL)) {
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
					cardSTATE_TO_IDLE();
					break;
				}
				LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
				cardINTREG = cardINTREG - ans;
				cardSTATE = MFEMUL_WORK;
				break;
			}
			case MFEMUL_INTREG_REST:{
				mf_crypto1_decrypt(pcs, receivedCmd, len);
				memcpy(&ans, receivedCmd, 4);
				if (emlGetValBl(&cardINTREG, &cardINTBLOCK, cardWRBL)) {
					EmSend4bit(mf_crypto1_encrypt4bit(pcs, CARD_NACK_NA));
					cardSTATE_TO_IDLE();
					break;
				}
				LogTrace(Uart.output, Uart.len, Uart.startTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.endTime*16 - DELAY_AIR2ARM_AS_TAG, Uart.parity, TRUE);
				cardSTATE = MFEMUL_WORK;
				break;
			}
		}
	}

	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
	LEDsoff();

	if(flags & FLAG_INTERACTIVE)// Interactive mode flag, means we need to send ACK
	{
		//May just aswell send the collected ar_nr in the response aswell
		uint8_t len = ar_nr_collected*5*4;
		cmd_send(CMD_ACK, CMD_SIMULATE_MIFARE_CARD, len, 0, &ar_nr_responses, len);
	}

	if(flags & FLAG_NR_AR_ATTACK && MF_DBGLEVEL >= 1 )
	{
		if(ar_nr_collected > 1 ) {
			Dbprintf("Collected two pairs of AR/NR which can be used to extract keys from reader:");
			Dbprintf("../tools/mfkey/mfkey32 %06x%08x %08x %08x %08x %08x %08x",
					ar_nr_responses[0], // UID1
					ar_nr_responses[1], // UID2
					ar_nr_responses[2], // NT
					ar_nr_responses[3], // AR1
					ar_nr_responses[4], // NR1
					ar_nr_responses[8], // AR2
					ar_nr_responses[9]  // NR2
					);
			Dbprintf("../tools/mfkey/mfkey32v2 %06x%08x %08x %08x %08x %08x %08x %08x",
					ar_nr_responses[0], // UID1
					ar_nr_responses[1], // UID2
					ar_nr_responses[2], // NT1
					ar_nr_responses[3], // AR1
					ar_nr_responses[4], // NR1
					ar_nr_responses[7], // NT2
					ar_nr_responses[8], // AR2
					ar_nr_responses[9]  // NR2
					);
		} else {
			Dbprintf("Failed to obtain two AR/NR pairs!");
			if(ar_nr_collected > 0 ) {
				Dbprintf("Only got these: UID=%07x%08x, nonce=%08x, AR1=%08x, NR1=%08x",
						ar_nr_responses[0], // UID1
						ar_nr_responses[1], // UID2
						ar_nr_responses[2], // NT
						ar_nr_responses[3], // AR1
						ar_nr_responses[4]  // NR1
						);
			}
		}
	}
	if (MF_DBGLEVEL >= 1)	Dbprintf("Emulator stopped. Tracing: %d  trace length: %d ", tracing, BigBuf_get_traceLen());
	
	set_tracing(FALSE);
}


//-----------------------------------------------------------------------------
// MIFARE sniffer. 
// 
//-----------------------------------------------------------------------------
void RAMFUNC SniffMifare(uint8_t param) {
	// param:
	// bit 0 - trigger from first card answer
	// bit 1 - trigger from first reader 7-bit request

	// C(red) A(yellow) B(green)
	LEDsoff();
	// init trace buffer
	clear_trace();
	set_tracing(TRUE);

	// The command (reader -> tag) that we're receiving.
	// The length of a received command will in most cases be no more than 18 bytes.
	// So 32 should be enough!
	uint8_t receivedCmd[MAX_MIFARE_FRAME_SIZE];
	uint8_t receivedCmdPar[MAX_MIFARE_PARITY_SIZE];
	// The response (tag -> reader) that we're receiving.
	uint8_t receivedResponse[MAX_MIFARE_FRAME_SIZE];
	uint8_t receivedResponsePar[MAX_MIFARE_PARITY_SIZE];

	iso14443a_setup(FPGA_HF_ISO14443A_SNIFFER);

	// free eventually allocated BigBuf memory
	BigBuf_free();
	// allocate the DMA buffer, used to stream samples from the FPGA
	uint8_t *dmaBuf = BigBuf_malloc(DMA_BUFFER_SIZE);
	uint8_t *data = dmaBuf;
	uint8_t previous_data = 0;
	int maxDataLen = 0;
	int dataLen = 0;
	bool ReaderIsActive = FALSE;
	bool TagIsActive = FALSE;

	// Set up the demodulator for tag -> reader responses.
	DemodInit(receivedResponse, receivedResponsePar);

	// Set up the demodulator for the reader -> tag commands
	UartInit(receivedCmd, receivedCmdPar);

	// Setup for the DMA.
	FpgaSetupSscDma((uint8_t *)dmaBuf, DMA_BUFFER_SIZE); // set transfer address and number of bytes. Start transfer.

	LED_D_OFF();
	
	// init sniffer
	MfSniffInit();

	// And now we loop, receiving samples.
	for(uint32_t sniffCounter = 0; TRUE; ) {
	
		if(BUTTON_PRESS()) {
			DbpString("cancelled by button");
			break;
		}

		LED_A_ON();
		WDT_HIT();
		
 		if ((sniffCounter & 0x0000FFFF) == 0) {	// from time to time
			// check if a transaction is completed (timeout after 2000ms).
			// if yes, stop the DMA transfer and send what we have so far to the client
			if (MfSniffSend(2000)) {			
				// Reset everything - we missed some sniffed data anyway while the DMA was stopped
				sniffCounter = 0;
				data = dmaBuf;
				maxDataLen = 0;
				ReaderIsActive = FALSE;
				TagIsActive = FALSE;
				FpgaSetupSscDma((uint8_t *)dmaBuf, DMA_BUFFER_SIZE); // set transfer address and number of bytes. Start transfer.
			}
		}
		
		int register readBufDataP = data - dmaBuf;	// number of bytes we have processed so far
		int register dmaBufDataP = DMA_BUFFER_SIZE - AT91C_BASE_PDC_SSC->PDC_RCR; // number of bytes already transferred
		if (readBufDataP <= dmaBufDataP){			// we are processing the same block of data which is currently being transferred
			dataLen = dmaBufDataP - readBufDataP;	// number of bytes still to be processed
		} else {									
			dataLen = DMA_BUFFER_SIZE - readBufDataP + dmaBufDataP; // number of bytes still to be processed
		}
		// test for length of buffer
		if(dataLen > maxDataLen) {					// we are more behind than ever...
			maxDataLen = dataLen;					
			if(dataLen > (9 * DMA_BUFFER_SIZE / 10)) {
				Dbprintf("blew circular buffer! dataLen=0x%x", dataLen);
				break;
			}
		}
		if(dataLen < 1) continue;

		// primary buffer was stopped ( <-- we lost data!
		if (!AT91C_BASE_PDC_SSC->PDC_RCR) {
			AT91C_BASE_PDC_SSC->PDC_RPR = (uint32_t) dmaBuf;
			AT91C_BASE_PDC_SSC->PDC_RCR = DMA_BUFFER_SIZE;
			Dbprintf("RxEmpty ERROR!!! data length:%d", dataLen); // temporary
		}
		// secondary buffer sets as primary, secondary buffer was stopped
		if (!AT91C_BASE_PDC_SSC->PDC_RNCR) {
			AT91C_BASE_PDC_SSC->PDC_RNPR = (uint32_t) dmaBuf;
			AT91C_BASE_PDC_SSC->PDC_RNCR = DMA_BUFFER_SIZE;
		}

		LED_A_OFF();
		
		if (sniffCounter & 0x01) {

			if(!TagIsActive) {		// no need to try decoding tag data if the reader is sending
				uint8_t readerdata = (previous_data & 0xF0) | (*data >> 4);
				if(MillerDecoding(readerdata, (sniffCounter-1)*4)) {
					LED_C_INV();
					if (MfSniffLogic(receivedCmd, Uart.len, Uart.parity, Uart.bitCount, TRUE)) break;

					/* And ready to receive another command. */
					UartReset();
					
					/* And also reset the demod code */
					DemodReset();
				}
				ReaderIsActive = (Uart.state != STATE_UNSYNCD);
			}
			
			if(!ReaderIsActive) {		// no need to try decoding tag data if the reader is sending
				uint8_t tagdata = (previous_data << 4) | (*data & 0x0F);
				if(ManchesterDecoding(tagdata, 0, (sniffCounter-1)*4)) {
					LED_C_INV();

					if (MfSniffLogic(receivedResponse, Demod.len, Demod.parity, Demod.bitCount, FALSE)) break;

					// And ready to receive another response.
					DemodReset();

					// And reset the Miller decoder including its (now outdated) input buffer
					UartInit(receivedCmd, receivedCmdPar);
					// why not UartReset?
				}
				TagIsActive = (Demod.state != DEMOD_UNSYNCD);
			}
		}

		previous_data = *data;
		sniffCounter++;
		data++;
		if(data == dmaBuf + DMA_BUFFER_SIZE) {
			data = dmaBuf;
		}

	} // main cycle

	FpgaDisableSscDma();
	MfSniffEnd();
	LEDsoff();
	Dbprintf("maxDataLen=%x, Uart.state=%x, Uart.len=%x", maxDataLen, Uart.state, Uart.len);
	set_tracing(FALSE);
}