]> git.zerfleddert.de Git - proxmark3-svn/blobdiff - armsrc/iso14443a.c
with the declaration of 'uint8_t destination[8]', 'destination' is already a pointer...
[proxmark3-svn] / armsrc / iso14443a.c
index 7c1db14ba842a3067f808fd09a0fffa71898d455..b3316ef0b637b617c707c2eb9017eab0ec8807fa 100644 (file)
@@ -88,25 +88,25 @@ void iso14a_set_timeout(uint32_t timeout) {
 //-----------------------------------------------------------------------------
 byte_t oddparity (const byte_t bt)
 {
-  return OddByteParity[bt];
+       return OddByteParity[bt];
 }
 
 uint32_t GetParity(const uint8_t * pbtCmd, int iLen)
 {
-  int i;
-  uint32_t dwPar = 0;
+       int i;
+       uint32_t dwPar = 0;
 
-  // Generate the encrypted data
-  for (i = 0; i < iLen; i++) {
-    // Save the encrypted parity bit
-    dwPar |= ((OddByteParity[pbtCmd[i]]) << i);
-  }
-  return dwPar;
+       // Generate the encrypted data
+       for (i = 0; i < iLen; i++) {
+               // Save the encrypted parity bit
+               dwPar |= ((OddByteParity[pbtCmd[i]]) << i);
+       }
+       return dwPar;
 }
 
 void AppendCrc14443a(uint8_t* data, int len)
 {
-  ComputeCrc14443(CRC_14443_A,data,len,data+len,data+len+1);
+       ComputeCrc14443(CRC_14443_A,data,len,data+len,data+len+1);
 }
 
 // The function LogTrace() is also used by the iClass implementation in iClass.c
@@ -584,7 +584,7 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
        
        LEDsoff();
        // init trace buffer
-    iso14a_clear_trace();
+       iso14a_clear_trace();
 
        // 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
@@ -775,54 +775,54 @@ static void CodeIso14443aAsTag(const uint8_t *cmd, int len){
        CodeIso14443aAsTagPar(cmd, len, GetParity(cmd, len));
 }
 
-//-----------------------------------------------------------------------------
-// This is to send a NACK kind of answer, its only 3 bits, I know it should be 4
-//-----------------------------------------------------------------------------
-static void CodeStrangeAnswerAsTag()
-{
-       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;
-
-       // 0
-       ToSend[++ToSendMax] = SEC_E;
-
-       // 0
-       ToSend[++ToSendMax] = SEC_E;
-
-       // 1
-       ToSend[++ToSendMax] = SEC_D;
-
-    // Send stopbit
-       ToSend[++ToSendMax] = SEC_F;
-
-       // Flush the buffer in FPGA!!
-       for(i = 0; i < 5; i++) {
-               ToSend[++ToSendMax] = SEC_F;
-       }
-
-    // Convert from last byte pos to length
-    ToSendMax++;
-}
+////-----------------------------------------------------------------------------
+//// This is to send a NACK kind of answer, its only 3 bits, I know it should be 4
+////-----------------------------------------------------------------------------
+//static void CodeStrangeAnswerAsTag()
+//{
+//     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;
+//
+//     // 0
+//     ToSend[++ToSendMax] = SEC_E;
+//
+//     // 0
+//     ToSend[++ToSendMax] = SEC_E;
+//
+//     // 1
+//     ToSend[++ToSendMax] = SEC_D;
+//
+//     // Send stopbit
+//     ToSend[++ToSendMax] = SEC_F;
+//
+//     // Flush the buffer in FPGA!!
+//     for(i = 0; i < 5; i++) {
+//             ToSend[++ToSendMax] = SEC_F;
+//     }
+//
+//     // Convert from last byte pos to length
+//     ToSendMax++;
+//}
 
 static void Code4bitAnswerAsTag(uint8_t cmd)
 {
        int i;
 
-    ToSendReset();
+       ToSendReset();
 
        // Correction bit, might be removed when not needed
        ToSendStuffBit(0);
@@ -855,8 +855,8 @@ static void Code4bitAnswerAsTag(uint8_t cmd)
                ToSend[++ToSendMax] = SEC_F;
        }
 
-    // Convert from last byte pos to length
-    ToSendMax++;
+       // Convert from last byte pos to length
+       ToSendMax++;
 }
 
 //-----------------------------------------------------------------------------
@@ -898,17 +898,86 @@ 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);
+
+static uint8_t* free_buffer_pointer = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);
+
+typedef struct {
+  uint8_t* response;
+  size_t   response_n;
+  uint8_t* modulation;
+  size_t   modulation_n;
+} tag_response_info_t;
+
+void reset_free_buffer() {
+  free_buffer_pointer = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);
+}
+
+bool prepare_tag_modulation(tag_response_info_t* response_info, size_t max_buffer_size) {
+       // Exmaple 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
+  response_info->modulation_n = ToSendMax;
+  
+  return true;
+}
+
+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 = (((uint8_t *)BigBuf)+FREE_BUFFER_OFFSET+FREE_BUFFER_SIZE)-free_buffer_pointer;
+  
+  // 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 uid_1st, int uid_2nd)
+void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd, byte_t* data)
 {
-  // Enable and clear the trace
+       // Enable and clear the trace
        tracing = TRUE;
-  iso14a_clear_trace();
+       iso14a_clear_trace();
 
        // This function contains the tag emulation
        uint8_t sak;
@@ -982,57 +1051,41 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
        ComputeCrc14443(CRC_14443_A, response3a, 1, &response3a[1], &response3a[2]);
 
        uint8_t response5[] = { 0x00, 0x00, 0x00, 0x00 }; // Very random tag nonce
-       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;
-       int respLen;
-
-  // Longest possible response will be 16 bytes + 2 CRC = 18 bytes
-       // This will need
-       //    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
-       //
-       // 166 bytes, since every bit that needs to be send costs us a byte
-       //
-
-       // Respond with card type
-       uint8_t *resp1 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET);
-       int resp1Len;
-
-       // Anticollision cascade1 - respond with uid
-       uint8_t *resp2 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + 166);
-       int resp2Len;
-
-       // Anticollision cascade2 - respond with 2nd half of uid if asked
-       // we're only going to be asked if we set the 1st byte of the UID (during cascade1) to 0x88
-       uint8_t *resp2a = (((uint8_t *)BigBuf) + 1140);
-       int resp2aLen;
-
-       // Acknowledge select - cascade 1
-       uint8_t *resp3 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*2));
-       int resp3Len;
-
-       // Acknowledge select - cascade 2
-       uint8_t *resp3a = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*3));
-       int resp3aLen;
-
-       // Response to a read request - not implemented atm
-       uint8_t *resp4 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*4));
-       int resp4Len;
-
-       // Authenticate response - nonce
-       uint8_t *resp5 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*5));
-       int resp5Len;
-
-       // Authenticate response - nonce
-       uint8_t *resp6 = (((uint8_t *)BigBuf) + FREE_BUFFER_OFFSET + (166*6));
-       int resp6Len;
+       uint8_t response6[] = { 0x04, 0x58, 0x00, 0x02, 0x00, 0x00 }; // dummy ATS (pseudo-ATR), answer to RATS
+       ComputeCrc14443(CRC_14443_A, response6, 4, &response6[4], &response6[5]);
+
+  #define TAG_RESPONSE_COUNT 7
+  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
+  };
+
+  // Allocate 512 bytes for the dynamic modulation, created when the reader querries 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
+  };
+  
+  // Reset the offset pointer of the free buffer
+  reset_free_buffer();
+  
+  // 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]);
+  }
 
        uint8_t *receivedCmd = (((uint8_t *)BigBuf) + RECV_CMD_OFFSET);
        int len;
@@ -1044,119 +1097,121 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
        // Just to allow some checks
        int happened = 0;
        int happened2 = 0;
-
        int cmdsRecvd = 0;
-       uint8_t* respdata = NULL;
-       int respsize = 0;
-       uint8_t nack = 0x04;
-
-       memset(receivedCmd, 0x44, RECV_CMD_SIZE);
-
-       // Prepare the responses of the anticollision phase
-       // there will be not enough time to do this at the moment the reader sends it REQA
-
-       // Answer to request
-       CodeIso14443aAsTag(response1, sizeof(response1));
-       memcpy(resp1, ToSend, ToSendMax); resp1Len = ToSendMax;
-
-       // Send our UID (cascade 1)
-       CodeIso14443aAsTag(response2, sizeof(response2));
-       memcpy(resp2, ToSend, ToSendMax); resp2Len = ToSendMax;
-
-       // Answer to select (cascade1)
-       CodeIso14443aAsTag(response3, sizeof(response3));
-       memcpy(resp3, ToSend, ToSendMax); resp3Len = ToSendMax;
-
-       // Send the cascade 2 2nd part of the uid
-       CodeIso14443aAsTag(response2a, sizeof(response2a));
-       memcpy(resp2a, ToSend, ToSendMax); resp2aLen = ToSendMax;
-
-       // Answer to select (cascade 2)
-       CodeIso14443aAsTag(response3a, sizeof(response3a));
-       memcpy(resp3a, ToSend, ToSendMax); resp3aLen = ToSendMax;
-
-       // Strange answer is an example of rare message size (3 bits)
-       CodeStrangeAnswerAsTag();
-       memcpy(resp4, ToSend, ToSendMax); resp4Len = ToSendMax;
-
-       // Authentication answer (random nonce)
-       CodeIso14443aAsTag(response5, sizeof(response5));
-       memcpy(resp5, ToSend, ToSendMax); resp5Len = ToSendMax;
-
-       // dummy ATS (pseudo-ATR), answer to RATS
-       CodeIso14443aAsTag(response6, sizeof(response6));
-       memcpy(resp6, ToSend, ToSendMax); resp6Len = ToSendMax;
 
        // We need to listen to the high-frequency, peak-detected path.
        SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
        FpgaSetupSsc();
 
        cmdsRecvd = 0;
+  tag_response_info_t* p_response;
 
        LED_A_ON();
        for(;;) {
+    // Clean receive command buffer
+    memset(receivedCmd, 0x44, RECV_CMD_SIZE);
        
                if(!GetIso14443aCommandFromReader(receivedCmd, &len, RECV_CMD_SIZE)) {
-                       DbpString("button press");
+                       DbpString("Button press");
                        break;
                }
+    
+               if (tracing) {
+                       LogTrace(receivedCmd,len, 0, Uart.parityBits, TRUE);
+               }
+    
+    p_response = NULL;
+    
                // 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;
                if(receivedCmd[0] == 0x26) { // Received a REQUEST
-                       resp = resp1; respLen = resp1Len; order = 1;
-                       respdata = response1;
-                       respsize = sizeof(response1);
+                       p_response = &responses[0]; order = 1;
                } else if(receivedCmd[0] == 0x52) { // Received a WAKEUP
-                       resp = resp1; respLen = resp1Len; order = 6;
-                       respdata = response1;
-                       respsize = sizeof(response1);
+                       p_response = &responses[0]; order = 6;
                } else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x93) {   // Received request for UID (cascade 1)
-                       resp = resp2; respLen = resp2Len; order = 2;
-                       respdata = response2;
-                       respsize = sizeof(response2);
+                       p_response = &responses[1]; order = 2;
                } else if(receivedCmd[1] == 0x20 && receivedCmd[0] == 0x95) { // Received request for UID (cascade 2)
-                       resp = resp2a; respLen = resp2aLen; order = 20;
-                       respdata = response2a;
-                       respsize = sizeof(response2a);
+                       p_response = &responses[2]; order = 20;
                } else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x93) {   // Received a SELECT (cascade 1)
-                       resp = resp3; respLen = resp3Len; order = 3;
-                       respdata = response3;
-                       respsize = sizeof(response3);
+                       p_response = &responses[3]; order = 3;
                } else if(receivedCmd[1] == 0x70 && receivedCmd[0] == 0x95) {   // Received a SELECT (cascade 2)
-                       resp = resp3a; respLen = resp3aLen; order = 30;
-                       respdata = response3a;
-                       respsize = sizeof(response3a);
+                       p_response = &responses[4]; order = 30;
                } else if(receivedCmd[0] == 0x30) {     // Received a (plain) READ
-                       resp = resp4; respLen = resp4Len; order = 4; // Do nothing
+                       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
+      p_response = NULL;
                } else if(receivedCmd[0] == 0x50) {     // Received a HALT
-                       DbpString("Reader requested we HALT!:");
-                       // Do not respond
-                       resp = resp1; respLen = 0; order = 0;
-                       respdata = NULL;
-                       respsize = 0;
+//                     DbpString("Reader requested we HALT!:");
+      p_response = NULL;
                } else if(receivedCmd[0] == 0x60 || receivedCmd[0] == 0x61) {   // Received an authentication request
-                       resp = resp5; respLen = resp5Len; order = 7;
-                       respdata = response5;
-                       respsize = sizeof(response5);
+                       p_response = &responses[5]; order = 7;
                } else if(receivedCmd[0] == 0xE0) {     // Received a RATS request
-                       resp = resp6; respLen = resp6Len; order = 70;
-                       respdata = response6;
-                       respsize = sizeof(response6);
-               } else {
-                       // Never seen this command before
-                       Dbprintf("Received (len=%d): %02x %02x %02x %02x %02x %02x %02x %02x %02x",
-                       len,
-                       receivedCmd[0], receivedCmd[1], receivedCmd[2],
-                       receivedCmd[3], receivedCmd[4], receivedCmd[5],
-                       receivedCmd[6], receivedCmd[7], receivedCmd[8]);
-                       // Do not respond
-                       resp = resp1; respLen = 0; order = 0;
-                       respdata = NULL;
-                       respsize = 0;
+                       p_response = &responses[6]; order = 70;
+               } else if (order == 7 && len ==8) { // Received authentication request
+      uint32_t nr = bytes_to_num(receivedCmd,4);
+      uint32_t ar = bytes_to_num(receivedCmd+4,4);
+      Dbprintf("Auth attempt {nr}{ar}: %08x %08x",nr,ar);
+    } else {
+      // Check for ISO 14443A-4 compliant commands, look at left nibble
+      switch (receivedCmd[0]) {
+
+        case 0x0B:
+        case 0x0A: { // IBlock (command)
+          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: { //
+          memcpy(dynamic_response_info.response,"\xAB\x00",2);
+          dynamic_response_info.response_n = 2;
+        } break;
+
+        case 0xCA:
+        case 0xC2: { // Readers sends deselect command
+          memcpy(dynamic_response_info.response,"\xCA\x00",2);
+          dynamic_response_info.response_n = 2;
+        } break;
+
+        default: {
+          // Never seen this command before
+          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");
+          break;
+        }
+        p_response = &dynamic_response_info;
+      }
                }
 
                // Count number of wakeups received after a halt
@@ -1174,138 +1229,97 @@ void SimulateIso14443aTag(int tagType, int uid_1st, int uid_2nd)
                if(cmdsRecvd > 999) {
                        DbpString("1000 commands later...");
                        break;
-               } else {
-                       cmdsRecvd++;
-               }
-
-               if(respLen > 0) {
-                       EmSendCmd14443aRaw(resp, respLen, receivedCmd[0] == 0x52);
                }
-               
-               if (tracing) {
-                       LogTrace(receivedCmd,len, 0, Uart.parityBits, TRUE);
-                       if (respdata != NULL) {
-                               LogTrace(respdata,respsize, 0, SwapBits(GetParity(respdata,respsize),respsize), FALSE);
-                       }
-                       if(traceLen > TRACE_SIZE) {
-                               DbpString("Trace full");
-                               break;
-                       }
-               }
-
-               memset(receivedCmd, 0x44, RECV_CMD_SIZE);
+               cmdsRecvd++;
+
+               if (p_response != NULL) {
+      EmSendCmd14443aRaw(p_response->modulation, p_response->modulation_n, receivedCmd[0] == 0x52);
+      if (tracing) {
+        LogTrace(p_response->response,p_response->response_n,0,SwapBits(GetParity(p_response->response,p_response->response_n),p_response->response_n),FALSE);
+        if(traceLen > TRACE_SIZE) {
+          DbpString("Trace full");
+//          break;
+        }
+      }
+    }
   }
 
        Dbprintf("%x %x %x", happened, happened2, cmdsRecvd);
        LED_A_OFF();
 }
 
-//-----------------------------------------------------------------------------
-// Transmit the command (to the tag) that was placed in ToSend[].
-//-----------------------------------------------------------------------------
-static void TransmitFor14443a(const uint8_t *cmd, int len, int *samples, int *wait)
-{
-  int c;
-
-  FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
-
-       if (wait)
-    if(*wait < 10)
-      *wait = 10;
-
-  for(c = 0; c < *wait;) {
-    if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-      AT91C_BASE_SSC->SSC_THR = 0x00;          // For exact timing!
-      c++;
-    }
-    if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-      volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
-      (void)r;
-    }
-    WDT_HIT();
-  }
 
-  c = 0;
-  for(;;) {
-    if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-      AT91C_BASE_SSC->SSC_THR = cmd[c];
-      c++;
-      if(c >= len) {
-        break;
-      }
-    }
-    if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
-      volatile uint32_t r = AT91C_BASE_SSC->SSC_RHR;
-      (void)r;
-    }
-    WDT_HIT();
-  }
-       if (samples) *samples = (c + *wait) << 3;
+// 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;
+               }
+       }
 }
 
 //-----------------------------------------------------------------------------
-// Code a 7-bit command without parity bit
-// This is especially for 0x26 and 0x52 (REQA and WUPA)
+// Transmit the command (to the tag) that was placed in ToSend[].
+// Parameter timing:
+// if NULL: ignored
+// if == 0:    return time of transfer
+// if != 0: delay transfer until time specified
 //-----------------------------------------------------------------------------
-void ShortFrameFromReader(const uint8_t bt)
+static void TransmitFor14443a(const uint8_t *cmd, int len, uint32_t *timing)
 {
-       int j;
-       int last;
-  uint8_t b;
+       int c;
 
-       ToSendReset();
+       FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
 
-       // 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;
+       if (timing) {
+               if(*timing == 0) {                                                                              // Measure time
+                       *timing = (GetCountMifare() + 8) & 0xfffffff8;
                } else {
-                       if(last == 0) {
-                               // Sequence Z
-                               ToSend[++ToSendMax] = SEC_Z;
-                       }
-                       else {
-                               // Sequence Y
-                               ToSend[++ToSendMax] = SEC_Y;
-                               last = 0;
-                       }
+                       PrepareDelayedTransfer(*timing & 0x00000007);           // Delay transfer (fine tuning - up to 7 MF clock ticks)
                }
-               b >>= 1;
+               if(MF_DBGLEVEL >= 4 && GetCountMifare() >= (*timing & 0xfffffff8)) Dbprintf("TransmitFor14443a: Missed timing");
+               while(GetCountMifare() < (*timing & 0xfffffff8));               // Delay transfer (multiple of 8 MF clock ticks)
        }
 
-       // End of Communication
-       if(last == 0) {
-               // Sequence Z
-               ToSend[++ToSendMax] = SEC_Z;
+       for(c = 0; c < 10;) {   // standard delay for each transfer (allow tag to be ready after last transmission)
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                       AT91C_BASE_SSC->SSC_THR = 0x00; 
+                       c++;
+               }
        }
-       else {
-               // Sequence Y
-               ToSend[++ToSendMax] = SEC_Y;
-               last = 0;
+       
+       c = 0;
+       for(;;) {
+               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                       AT91C_BASE_SSC->SSC_THR = cmd[c];
+                       c++;
+                       if(c >= len) {
+                               break;
+                       }
+               }
        }
-       // 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
-//
+// Prepare reader command (in bits, support short frames) 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;
@@ -1317,12 +1331,14 @@ 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;
@@ -1340,19 +1356,22 @@ 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;
+        }
       }
     }
   }
@@ -1378,6 +1397,14 @@ 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)
@@ -1543,7 +1570,7 @@ 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;
@@ -1556,10 +1583,10 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, int maxLen, int
        for(;;) {
                WDT_HIT();
 
-               if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
-                       AT91C_BASE_SSC->SSC_THR = 0x00;  // To make use of exact timing of next command from reader!!
-                       if (elapsed) (*elapsed)++;
-               }
+               // if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
+                       // AT91C_BASE_SSC->SSC_THR = 0x00;  // To make use of exact timing of next command from reader!!
+                       // if (elapsed) (*elapsed)++;
+               // }
                if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
                        if(c < iso14a_timeout) { c++; } else { return FALSE; }
                        b = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
@@ -1575,43 +1602,29 @@ 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, uint32_t *timing)
 {
-  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);
+  TransmitFor14443a(ToSend, ToSendMax, timing);
   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, uint32_t *timing)
+{
+  ReaderTransmitBitsPar(frame,len*8,par, timing);
+}
 
-void ReaderTransmit(uint8_t* frame, int len)
+void ReaderTransmit(uint8_t* frame, int len, uint32_t *timing)
 {
   // Generate parity and redirect
-  ReaderTransmitPar(frame,len,GetParity(frame,len));
+  ReaderTransmitBitsPar(frame,len*8,GetParity(frame,len), timing);
 }
 
 int ReaderReceive(uint8_t* receivedAnswer)
@@ -1637,117 +1650,116 @@ 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, NULL);
+  // 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);
   }
-       
+
   // clear uid
   if (uid_ptr) {
     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;
-    
-    // First backup the current uid 
+    // SELECT_ALL
+    ReaderTransmit(sel_all,sizeof(sel_all), NULL);
+    if (!ReaderReceive(resp)) return 0;
+
+    // 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]);
-    
-               // calculate crypto UID
-               if(cuid_ptr) {
-      *cuid_ptr = bytes_to_num(uid_resp, 4);
+
+        // calculate crypto UID. Always use last 4 Bytes.
+    if(cuid_ptr) {
+        *cuid_ptr = bytes_to_num(uid_resp, 4);
     }
 
-               // Construct SELECT UID command
-               memcpy(sel_uid+2,resp,5);
-               AppendCrc14443a(sel_uid,7);
-               ReaderTransmit(sel_uid,sizeof(sel_uid));
+    // Construct SELECT UID command
+    memcpy(sel_uid+2,resp,5);
+    AppendCrc14443a(sel_uid,7);
+    ReaderTransmit(sel_uid,sizeof(sel_uid), NULL);
 
-               // 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;
     }
-    
+
     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;
-       }
+  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;
-       }
-       
-       // reset the PCB block number
-       iso14_pcb_blocknum = 0;
-       return 1;
+  // Request for answer to select
+  AppendCrc14443a(rats, 2);
+  ReaderTransmit(rats, sizeof(rats), NULL);
+
+  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;
 }
 
 void iso14443a_setup() {
-  // Set up the synchronous serial port
-  FpgaSetupSsc();
+       // Set up the synchronous serial port
+       FpgaSetupSsc();
        // Start from off (no field generated)
        // Signal field is off with the appropriate LED
-       LED_D_OFF();
-       FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
-       SpinDelay(50);
+//     LED_D_OFF();
+//     FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+       // SpinDelay(50);
 
        SetAdcMuxFor(GPIO_MUXSEL_HIPKD);
 
@@ -1755,7 +1767,7 @@ void iso14443a_setup() {
        // Signal field is on with the appropriate LED
        LED_D_ON();
        FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
-       SpinDelay(50);
+       SpinDelay(7); // iso14443-3 specifies 5ms max.
 
        iso14a_timeout = 2048; //default
 }
@@ -1769,7 +1781,7 @@ int iso14_apdu(uint8_t * cmd, size_t cmd_len, void * data) {
        memcpy(real_cmd+2, cmd, cmd_len);
        AppendCrc14443a(real_cmd,cmd_len+2);
  
-       ReaderTransmit(real_cmd, cmd_len+4);
+       ReaderTransmit(real_cmd, cmd_len+4, NULL);
        size_t len = ReaderReceive(data);
        uint8_t * data_bytes = (uint8_t *) data;
        if (!len)
@@ -1796,21 +1808,26 @@ void ReaderIso14443a(UsbCommand * c)
        iso14a_command_t param = c->arg[0];
        uint8_t * cmd = c->d.asBytes;
        size_t len = c->arg[1];
-  uint32_t arg0 = 0;
-  byte_t buf[USB_CMD_DATA_SIZE];
+       size_t lenbits = c->arg[2];
+       uint32_t arg0 = 0;
+       byte_t buf[USB_CMD_DATA_SIZE];
   
-  iso14a_clear_trace();
-  iso14a_set_tracing(true);
+       if(param & ISO14A_CONNECT) {
+               iso14a_clear_trace();
+       }
+       iso14a_set_tracing(true);
 
        if(param & ISO14A_REQUEST_TRIGGER) {
-    iso14a_set_trigger(1);
-  }
+               iso14a_set_trigger(1);
+       }
 
        if(param & ISO14A_CONNECT) {
                iso14443a_setup();
-               arg0 = iso14443a_select_card(NULL,(iso14a_card_select_t*)buf,NULL);
-               cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(iso14a_card_select_t));
-//    UsbSendPacket((void *)ack, sizeof(UsbCommand));
+               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) {
@@ -1824,7 +1841,6 @@ void ReaderIso14443a(UsbCommand * c)
        if(param & ISO14A_APDU) {
                arg0 = iso14_apdu(cmd, len, buf);
                cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
-//             UsbSendPacket((void *)ack, sizeof(UsbCommand));
        }
 
        if(param & ISO14A_RAW) {
@@ -1832,105 +1848,212 @@ void ReaderIso14443a(UsbCommand * c)
                        AppendCrc14443a(cmd,len);
                        len += 2;
                }
-               ReaderTransmit(cmd,len);
+               if(lenbits>0) {
+                       ReaderTransmitBitsPar(cmd,lenbits,GetParity(cmd,lenbits/8), NULL);
+               } else {
+                       ReaderTransmit(cmd,len, NULL);
+               }
                arg0 = ReaderReceive(buf);
-//             UsbSendPacket((void *)ack, sizeof(UsbCommand));
-    cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
+               cmd_send(CMD_ACK,arg0,0,0,buf,sizeof(buf));
        }
 
        if(param & ISO14A_REQUEST_TRIGGER) {
-    iso14a_set_trigger(0);
-  }
+               iso14a_set_trigger(0);
+       }
 
        if(param & ISO14A_NO_DISCONNECT) {
                return;
-  }
+       }
 
        FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
        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 < 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();
+               while((GetCountMifare() & 0xffff0000) != 0x10000);              // wait for counter to reset and "warm up" 
+               sync_time = GetCountMifare() & 0xfffffff8;
+               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)) {
+                       if (MF_DBGLEVEL >= 1)   Dbprintf("Mifare: Can't select card");
+                       continue;
+               }
 
-               // Transmit MIFARE_CLASSIC_AUTH
-               ReaderTransmit(mf_auth, sizeof(mf_auth));
+               //keep the card active
+               FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_ISO14443A | FPGA_HF_ISO14443A_READER_MOD);
 
-               // Receive the (16 bit) "random" nonce
-               if (!ReaderReceive(receivedAnswer)) continue;
-               memcpy(nt, receivedAnswer, 4);
+               // CodeIso14443aBitsAsReaderPar(mf_auth, sizeof(mf_auth)*8, GetParity(mf_auth, sizeof(mf_auth)*8));
 
-               // Transmit reader nonce and reader answer
-               ReaderTransmitPar(mf_nr_ar, sizeof(mf_nr_ar),par);
+               sync_time = (sync_time & 0xfffffff8) + sync_cycles + catch_up_cycles;
+               catch_up_cycles = 0;
 
-               // Receive 4 bit answer
-               if (ReaderReceive(receivedAnswer))
-               {
-                       if ( (parameter != 0) && (memcmp(nt, nt_noattack, 4) == 0) ) continue;
+               // if we missed the sync time already, advance to the next nonce repeat
+               while(GetCountMifare() > sync_time) {
+                       sync_time = (sync_time & 0xfffffff8) + sync_cycles;
+               }
 
-                       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;
+               // Transmit MIFARE_CLASSIC_AUTH at synctime. Should result in returning the same tag nonce (== nt_attacked) 
+               ReaderTransmit(mf_auth, sizeof(mf_auth), &sync_time);
+
+               // Receive the (4 Byte) "random" nonce
+               if (!ReaderReceive(receivedAnswer)) {
+                       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, try again
+                                       continue;
+                               }
+                               sync_cycles = (sync_cycles - nt_distance);
+                               if (MF_DBGLEVEL >= 3) 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) {
+                               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);
+                       }
+                       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 is delayed by 8 cycles due to the NAC (4Bits = 0x05 encrypted) transfer
+       
                        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;
 
@@ -1941,10 +2064,10 @@ 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 {
@@ -1953,31 +2076,27 @@ 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. 
 // 
@@ -2554,4 +2673,4 @@ 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
+}
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