]> git.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/iso14443a.c
improve hf mf sim x reader attack
[proxmark3-svn] / armsrc / iso14443a.c
index 0431876eca41eb756342de78d8a3e58a75711f78..4f0a990f3df68276fdd38ccea44c2ef5dda250c3 100644 (file)
@@ -213,6 +213,12 @@ 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
 //=============================================================================
@@ -232,13 +238,17 @@ void AppendCrc14443a(uint8_t* data, int len)
 static tUart Uart;
 
 // Lookup-Table to decide if 4 raw bits are a modulation.
-// We accept two or three consecutive "0" in any position with the rest "1"
+// 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[] = {
-       TRUE,  TRUE,  FALSE, TRUE,  FALSE, FALSE, FALSE, FALSE,
-       TRUE,  TRUE,  FALSE, FALSE, TRUE,  FALSE, FALSE, FALSE
+       FALSE,  TRUE, FALSE, TRUE,  FALSE, FALSE, FALSE, TRUE,
+       FALSE,  TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE
 };
-#define IsMillerModulationNibble1(b) (Mod_Miller_LUT[(b & 0x00F0) >> 4])
-#define IsMillerModulationNibble2(b) (Mod_Miller_LUT[(b & 0x000F)])
+#define IsMillerModulationNibble1(b) (Mod_Miller_LUT[(b & 0x000000F0) >> 4])
+#define IsMillerModulationNibble2(b) (Mod_Miller_LUT[(b & 0x0000000F)])
 
 void UartReset()
 {
@@ -248,8 +258,6 @@ void UartReset()
        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.twoBits = 0x0000;                          // buffer for 2 Bits
-       Uart.highCnt = 0;
        Uart.startTime = 0;
        Uart.endTime = 0;
 }
@@ -258,6 +266,7 @@ void UartInit(uint8_t *data, uint8_t *parity)
 {
        Uart.output = data;
        Uart.parity = parity;
+       Uart.fourBits = 0x00000000;                     // clear the buffer for 4 Bits
        UartReset();
 }
 
@@ -265,40 +274,37 @@ void UartInit(uint8_t *data, uint8_t *parity)
 static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
 {
 
-       Uart.twoBits = (Uart.twoBits << 8) | bit;
+       Uart.fourBits = (Uart.fourBits << 8) | bit;
        
        if (Uart.state == STATE_UNSYNCD) {                                                                                      // not yet synced
        
-               if (Uart.highCnt < 2) {                                                                                                 // wait for a stable unmodulated signal
-                       if (Uart.twoBits == 0xffff) {
-                               Uart.highCnt++;
-                       } else {
-                               Uart.highCnt = 0;
-                       }
-               } else {        
-                       Uart.syncBit = 0xFFFF;                                                                                          // not set
-                                                                                                                                                               // we look for a ...1111111100x11111xxxxxx pattern (the start bit)
-                       if              ((Uart.twoBits & 0xDF00) == 0x1F00) Uart.syncBit = 8;           // mask is   11x11111 xxxxxxxx, 
-                                                                                                                                                               // check for 00x11111 xxxxxxxx
-                       else if ((Uart.twoBits & 0xEF80) == 0x8F80) Uart.syncBit = 7;           // both masks shifted right one bit, left padded with '1'
-                       else if ((Uart.twoBits & 0xF7C0) == 0xC7C0) Uart.syncBit = 6;           // ...
-                       else if ((Uart.twoBits & 0xFBE0) == 0xE3E0) Uart.syncBit = 5;
-                       else if ((Uart.twoBits & 0xFDF0) == 0xF1F0) Uart.syncBit = 4;
-                       else if ((Uart.twoBits & 0xFEF8) == 0xF8F8) Uart.syncBit = 3;
-                       else if ((Uart.twoBits & 0xFF7C) == 0xFC7C) Uart.syncBit = 2;
-                       else if ((Uart.twoBits & 0xFFBE) == 0xFE3E) Uart.syncBit = 1;
-                       if (Uart.syncBit != 0xFFFF) {                                                                           // 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;
-                       }
+               Uart.syncBit = 9999;                                                                                                    // not set
+               // 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 ...xx11111111111100x11111xxxxxx... 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    00000111 11111111 11101111 10000000
+               #define ISO14443A_STARTBIT_PATTERN      0x07FF8F80                                                      // pattern is 00000111 11111111 10001111 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.twoBits >> Uart.syncBit)) {                  
-                       if (IsMillerModulationNibble2(Uart.twoBits >> Uart.syncBit)) {          // Modulation in both halves - error
+               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
@@ -322,7 +328,7 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
                                }
                        }
                } else {
-                       if (IsMillerModulationNibble2(Uart.twoBits >> Uart.syncBit)) {          // Modulation second half = Sequence X = logic "1"
+                       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;
@@ -358,12 +364,10 @@ static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
                                                return TRUE;                                                                                    // we are finished with decoding the raw data sequence
                                        } else {
                                                UartReset();                                                                                    // Nothing received - start over
-                                               Uart.highCnt = 1;
                                        }
                                }
                                if (Uart.state == STATE_START_OF_COMMUNICATION) {                               // error - must not follow directly after SOC
                                        UartReset();
-                                       Uart.highCnt = 1;
                                } else {                                                                                                                // a logic "0"
                                        Uart.bitCount++;
                                        Uart.shiftReg = (Uart.shiftReg >> 1);                                           // add a 0 to the shiftreg
@@ -680,6 +684,9 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
 
                                        // 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);
@@ -1336,7 +1343,7 @@ void CodeIso14443aBitsAsReaderPar(const uint8_t *cmd, uint16_t bits, const uint8
                }
 
                // Only transmit parity bit if we transmitted a complete byte
-               if (j == 8) {
+               if (j == 8 && parity != NULL) {
                        // Get the parity bit
                        if (parity[i>>3] & (0x80 >> (i&0x0007))) {
                                // Sequence X
@@ -1630,6 +1637,7 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receive
        }
 }
 
+
 void ReaderTransmitBitsPar(uint8_t* frame, uint16_t bits, uint8_t *par, uint32_t *timing)
 {
        CodeIso14443aBitsAsReaderPar(frame, bits, par);
@@ -1645,11 +1653,13 @@ void ReaderTransmitBitsPar(uint8_t* frame, uint16_t bits, uint8_t *par, uint32_t
        }
 }
 
+
 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
@@ -1658,6 +1668,7 @@ void ReaderTransmitBits(uint8_t* frame, uint16_t len, uint32_t *timing)
   ReaderTransmitBitsPar(frame, len, par, timing);
 }
 
+
 void ReaderTransmit(uint8_t* frame, uint16_t len, uint32_t *timing)
 {
   // Generate parity and redirect
@@ -1718,6 +1729,11 @@ int iso14443a_select_card(byte_t *uid_ptr, iso14a_card_select_t *p_hi14a_card, u
                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.
@@ -1926,15 +1942,38 @@ void ReaderIso14443a(UsbCommand *c)
 
        if(param & ISO14A_RAW) {
                if(param & ISO14A_APPEND_CRC) {
-                       AppendCrc14443a(cmd,len);
+                       if(param & ISO14A_TOPAZMODE) {
+                               AppendCrc14443b(cmd,len);
+                       } else {
+                               AppendCrc14443a(cmd,len);
+                       }
                        len += 2;
                        if (lenbits) lenbits += 16;
                }
-               if(lenbits>0) {
-                       GetParity(cmd, lenbits/8, par);
-                       ReaderTransmitBitsPar(cmd, lenbits, par, NULL);
-               } else {
-                       ReaderTransmit(cmd,len, NULL);
+               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));
@@ -2018,9 +2057,10 @@ void ReaderMifare(bool first_try)
 
        #define PRNG_SEQUENCE_LENGTH  (1 << 16);
        static uint32_t sync_time;
-       static uint32_t sync_cycles;
+       static int32_t sync_cycles;
        int catch_up_cycles = 0;
        int last_catch_up = 0;
+       uint16_t elapsed_prng_sequences;
        uint16_t consecutive_resyncs = 0;
        int isOK = 0;
 
@@ -2029,7 +2069,6 @@ void ReaderMifare(bool first_try)
                sync_time = GetCountSspClk() & 0xfffffff8;
                sync_cycles = PRNG_SEQUENCE_LENGTH;                                                     // theory: Mifare Classic's random generator repeats every 2^16 cycles (and so do the tag nonces).
                nt_attacked = 0;
-               nt = 0;
                par[0] = 0;
        }
        else {
@@ -2045,11 +2084,16 @@ void ReaderMifare(bool first_try)
        
 
        #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                  16
+       #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;
-       uint32_t debug_info[MAX_SYNC_TRIES];
+       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++) {
                
@@ -2062,24 +2106,59 @@ void ReaderMifare(bool first_try)
                        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 {
-                       ReaderTransmit(mf_auth, sizeof(mf_auth), NULL);
+                       // 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
@@ -2101,7 +2180,7 @@ void ReaderMifare(bool first_try)
                        } else {
                                if (nt_distance == -99999) { // invalid nonce received
                                        unexpected_random++;
-                                       if (!nt_attacked && unexpected_random > MAX_UNEXPECTED_RANDOM) {
+                                       if (unexpected_random > MAX_UNEXPECTED_RANDOM) {
                                                isOK = -3;              // Card has an unpredictable PRNG. Give up      
                                                break;
                                        } else {
@@ -2109,20 +2188,25 @@ void ReaderMifare(bool first_try)
                                        }
                                }
                                if (++sync_tries > MAX_SYNC_TRIES) {
-                                       if (sync_tries > 2 * 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[++debug_info_nr] = nt_distance;
+                                               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);
+                               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, Sync_cycles: %d\n", i, nt_distance, sync_cycles);
+                                       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;
                        }
@@ -2134,6 +2218,7 @@ void ReaderMifare(bool first_try)
                                catch_up_cycles = 0;
                                continue;
                        }
+                       catch_up_cycles /= elapsed_prng_sequences;
                        if (catch_up_cycles == last_catch_up) {
                                consecutive_resyncs++;
                        }
@@ -2147,6 +2232,9 @@ void ReaderMifare(bool first_try)
                        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;
                }
@@ -2154,12 +2242,10 @@ void ReaderMifare(bool first_try)
                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))
-               {
+               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)
-                       {
+                       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
                        }
 
@@ -2197,8 +2283,10 @@ void ReaderMifare(bool first_try)
 
        if (isOK == -4) {
                if (MF_DBGLEVEL >= 3) {
-                       for(uint16_t i = 0; i < MAX_SYNC_TRIES; i++) {
-                               Dbprintf("collected debug info[%d] = %d\n", i, debug_info[i]);
+                       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]);
+                               }
                        }
                }
        }
@@ -2219,6 +2307,18 @@ void ReaderMifare(bool first_try)
        set_tracing(FALSE);
 }
 
+typedef struct {
+  uint32_t cuid;
+  uint8_t  sector;
+  uint8_t  keytype;
+  uint32_t nonce;
+  uint32_t ar;
+  uint32_t nr;
+  uint32_t nonce2;
+  uint32_t ar2;
+  uint32_t nr2;
+} nonces_t;
+
 /**
   *MIFARE 1K simulate.
   *
@@ -2265,12 +2365,18 @@ void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *
        uint8_t rAUTH_NT[] = {0x01, 0x02, 0x03, 0x04};
        uint8_t rAUTH_AT[] = {0x00, 0x00, 0x00, 0x00};
                
-       //Here, we collect UID,NT,AR,NR,UID2,NT2,AR2,NR2
+       //Here, we collect UID,sector,keytype,NT,AR,NR,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};
-       uint8_t ar_nr_collected = 0;
-
+       
+       //allow collecting up to 4 sets of nonces to allow recovery of 4 keys (2 keyA & 2 keyB)
+       // must be set in multiples of 2 (for 1 keyA and 1 keyB)
+       #define ATTACK_KEY_COUNT 4
+       nonces_t ar_nr_resp[ATTACK_KEY_COUNT]; 
+       memset(ar_nr_resp, 0x00, sizeof(ar_nr_resp));
+
+       uint8_t ar_nr_collected[ATTACK_KEY_COUNT];
+       memset(ar_nr_collected, 0x00, sizeof(ar_nr_collected));
        // Authenticate response - nonce
        uint32_t nonce = bytes_to_num(rAUTH_NT, 4);
        
@@ -2418,16 +2524,35 @@ void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *
 
                                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){
-                                       if(ar_nr_responses[2] != ar)
-                                       {// Avoid duplicates... probably not necessary, ar should vary. 
-                                               ar_nr_responses[ar_nr_collected*4] = cuid;
-                                               ar_nr_responses[ar_nr_collected*4+1] = nonce;
-                                               ar_nr_responses[ar_nr_collected*4+2] = ar;
-                                               ar_nr_responses[ar_nr_collected*4+3] = nr;
-                                               ar_nr_collected++;
+       
+                               //Collect AR/NR per key/sector
+                               if(flags & FLAG_NR_AR_ATTACK) {
+                                       for (uint8_t i = 0; i < ATTACK_KEY_COUNT; i++) {
+                                               if(cardAUTHKEY > 0 && i < (ATTACK_KEY_COUNT/2) ) {
+                                                       i=ATTACK_KEY_COUNT/2;  //keyB skip to keyB
+                                               } else if (cardAUTHKEY == 0 && i == ATTACK_KEY_COUNT/2) {
+                                                       break; //should not get here - quit
+                                               }
+                                               // if first auth for sector, or matches sector of previous auth
+                                               if ( ar_nr_collected[i]==0 || (cardAUTHSC == ar_nr_resp[i].sector && ar_nr_collected[i] > 0) ) {
+                                                       if(ar_nr_collected[i] < 2) {
+                                                               if(ar_nr_resp[ar_nr_collected[i]].ar != ar)
+                                                               {// Avoid duplicates... probably not necessary, ar should vary. 
+                                                                       if (ar_nr_collected[i]==0) {
+                                                                               ar_nr_resp[i].cuid = cuid;
+                                                                               ar_nr_resp[i].sector = cardAUTHSC;
+                                                                               ar_nr_resp[i].nonce = nonce;
+                                                                               ar_nr_resp[i].ar = ar;
+                                                                               ar_nr_resp[i].nr = nr;
+                                                                       } else {
+                                                                               ar_nr_resp[i].ar2 = ar;
+                                                                               ar_nr_resp[i].nr2 = nr;
+                                                                       }
+                                                                       ar_nr_collected[i]++;
+                                                                       break;
+                                                               }
+                                                       }
+                                               }
                                        }
                                }
 
@@ -2449,6 +2574,7 @@ void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *
                                        break;
                                }
 
+                               //auth successful
                                ans = prng_successor(nonce, 96) ^ crypto1_word(pcs, 0, 0);
 
                                num_to_bytes(ans, 4, rAUTH_AT);
@@ -2692,37 +2818,29 @@ void Mifare1ksim(uint8_t flags, uint8_t exitAfterNReads, uint8_t arg2, uint8_t *
        FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
        LEDsoff();
 
-       if(flags & FLAG_INTERACTIVE)// Interactive mode flag, means we need to send ACK
+       if(flags & FLAG_NR_AR_ATTACK && MF_DBGLEVEL >= 1)
        {
-               //May just aswell send the collected ar_nr in the response aswell
-               cmd_send(CMD_ACK,CMD_SIMULATE_MIFARE_CARD,0,0,&ar_nr_responses,ar_nr_collected*4*4);
-       }
-
-       if(flags & FLAG_NR_AR_ATTACK)
-       {
-               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 %08x %08x %08x %08x %08x %08x",
-                                       ar_nr_responses[0], // UID
-                                       ar_nr_responses[1], //NT
-                                       ar_nr_responses[2], //AR1
-                                       ar_nr_responses[3], //NR1
-                                       ar_nr_responses[6], //AR2
-                                       ar_nr_responses[7] //NR2
-                                       );
-               } else {
-                       Dbprintf("Failed to obtain two AR/NR pairs!");
-                       if(ar_nr_collected >0) {
-                               Dbprintf("Only got these: UID=%08x, nonce=%08x, AR1=%08x, NR1=%08x",
-                                               ar_nr_responses[0], // UID
-                                               ar_nr_responses[1], //NT
-                                               ar_nr_responses[2], //AR1
-                                               ar_nr_responses[3] //NR1
+               for ( uint8_t   i = 0; i < ATTACK_KEY_COUNT; i++) {
+                       if (ar_nr_collected[i] == 2) {
+                               Dbprintf("Collected two pairs of AR/NR which can be used to extract %s from reader for sector %d:", (i<ATTACK_KEY_COUNT/2) ? "keyA" : "keyB", ar_nr_resp[i].sector);
+                               Dbprintf("../tools/mfkey/mfkey32 %08x %08x %08x %08x %08x %08x",
+                                               ar_nr_resp[i].cuid,  //UID
+                                               ar_nr_resp[i].nonce, //NT
+                                               ar_nr_resp[i].ar,    //AR1
+                                               ar_nr_resp[i].nr,    //NR1
+                                               ar_nr_resp[i].ar2,   //AR2
+                                               ar_nr_resp[i].nr2    //NR2
                                                );
                        }
-               }
+               }       
        }
        if (MF_DBGLEVEL >= 1)   Dbprintf("Emulator stopped. Tracing: %d  trace length: %d ",    tracing, BigBuf_get_traceLen());
+
+       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
+               cmd_send(CMD_ACK,CMD_SIMULATE_MIFARE_CARD,0,0,&ar_nr_resp,sizeof(ar_nr_resp));
+       }
        
 }
 
@@ -2844,7 +2962,7 @@ void RAMFUNC SniffMifare(uint8_t param) {
                                        if (MfSniffLogic(receivedCmd, Uart.len, Uart.parity, Uart.bitCount, TRUE)) break;
 
                                        /* And ready to receive another command. */
-                                       UartReset();
+                                       UartInit(receivedCmd, receivedCmdPar);
                                        
                                        /* And also reset the demod code */
                                        DemodReset();
@@ -2861,6 +2979,8 @@ void RAMFUNC SniffMifare(uint8_t param) {
 
                                        // And ready to receive another response.
                                        DemodReset();
+                                       // And reset the Miller decoder including its (now outdated) input buffer
+                                       UartInit(receivedCmd, receivedCmdPar);
                                }
                                TagIsActive = (Demod.state != DEMOD_UNSYNCD);
                        }
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