int tryDecryptWord(uint32_t nt, uint32_t ar_enc, uint32_t at_enc, uint8_t *data, int len){
/*
uint32_t nt; // tag challenge
uint32_t nr_enc; // encrypted reader challenge
uint32_t ar_enc; // encrypted reader response
uint32_t at_enc; // encrypted tag response
*/
struct Crypto1State *pcs = NULL;
ks2 = ar_enc ^ prng_successor(nt, 64);
ks3 = at_enc ^ prng_successor(nt, 96);
PrintAndLog("Decrypting data with:");
PrintAndLog(" nt: %08x",nt);
PrintAndLog(" ar_enc: %08x",ar_enc);
PrintAndLog(" at_enc: %08x",at_enc);
PrintAndLog("\nEncrypted data: [%s]", sprint_hex(data,len) );
pcs = lfsr_recovery64(ks2, ks3);
mf_crypto1_decrypt(pcs, data, len, FALSE);
PrintAndLog("Decrypted data: [%s]", sprint_hex(data,len) );
crypto1_destroy(pcs);
return 0;
}
int mfTraceDecode(uint8_t *data_src, int len, bool wantSaveToEmlFile) {
uint8_t data[64];
if (traceState == TRACE_ERROR) return 1;
if (len > 64) {
traceState = TRACE_ERROR;
return 1;
}
memcpy(data, data_src, len);
if ((traceCrypto1) && ((traceState == TRACE_IDLE) || (traceState > TRACE_AUTH_OK))) {
mf_crypto1_decrypt(traceCrypto1, data, len, 0);
PrintAndLog("dec> %s", sprint_hex(data, len));
AddLogHex(logHexFileName, "dec> ", data, len);
}
switch (traceState) {
case TRACE_IDLE:
// check packet crc16!
if ((len >= 4) && (!CheckCrc14443(CRC_14443_A, data, len))) {
PrintAndLog("dec> CRC ERROR!!!");
AddLogLine(logHexFileName, "dec> ", "CRC ERROR!!!");
traceState = TRACE_ERROR; // do not decrypt the next commands
return 1;
}
// AUTHENTICATION
if ((len == 4) && ((data[0] == 0x60) || (data[0] == 0x61))) {
traceState = TRACE_AUTH1;
traceCurBlock = data[1];
traceCurKey = data[0] == 60 ? 1:0;
return 0;
}
// READ
if ((len ==4) && ((data[0] == 0x30))) {
traceState = TRACE_READ_DATA;
traceCurBlock = data[1];
return 0;
}
// WRITE
if ((len ==4) && ((data[0] == 0xA0))) {
traceState = TRACE_WRITE_OK;
traceCurBlock = data[1];
return 0;
}
// HALT
if ((len ==4) && ((data[0] == 0x50) && (data[1] == 0x00))) {
traceState = TRACE_ERROR; // do not decrypt the next commands
return 0;
}
return 0;
break;
case TRACE_READ_DATA:
if (len == 18) {
traceState = TRACE_IDLE;
if (isBlockTrailer(traceCurBlock)) {
memcpy(traceCard + traceCurBlock * 16 + 6, data + 6, 4);
} else {
memcpy(traceCard + traceCurBlock * 16, data, 16);
}
if (wantSaveToEmlFile) saveTraceCard();
return 0;
} else {
traceState = TRACE_ERROR;
return 1;
}
break;
case TRACE_WRITE_OK:
if ((len == 1) && (data[0] == 0x0a)) {
traceState = TRACE_WRITE_DATA;
return 0;
} else {
traceState = TRACE_ERROR;
return 1;
}
break;
case TRACE_WRITE_DATA:
if (len == 18) {
traceState = TRACE_IDLE;
memcpy(traceCard + traceCurBlock * 16, data, 16);
if (wantSaveToEmlFile) saveTraceCard();
return 0;
} else {
traceState = TRACE_ERROR;
return 1;
}
break;
case TRACE_AUTH1:
if (len == 4) {
traceState = TRACE_AUTH2;
nt = bytes_to_num(data, 4);
return 0;
} else {
traceState = TRACE_ERROR;
return 1;
}
break;
case TRACE_AUTH2:
if (len == 8) {
traceState = TRACE_AUTH_OK;
nr_enc = bytes_to_num(data, 4);
ar_enc = bytes_to_num(data + 4, 4);
return 0;
} else {
traceState = TRACE_ERROR;
return 1;
}
break;
case TRACE_AUTH_OK:
if (len ==4) {
traceState = TRACE_IDLE;
at_enc = bytes_to_num(data, 4);
// decode key here)
ks2 = ar_enc ^ prng_successor(nt, 64);
ks3 = at_enc ^ prng_successor(nt, 96);
revstate = lfsr_recovery64(ks2, ks3);
lfsr_rollback_word(revstate, 0, 0);
lfsr_rollback_word(revstate, 0, 0);
lfsr_rollback_word(revstate, nr_enc, 1);
lfsr_rollback_word(revstate, uid ^ nt, 0);
crypto1_get_lfsr(revstate, &key);
printf("Key: %012"llx"\n",key);
AddLogUint64(logHexFileName, "key: ", key);
int blockShift = ((traceCurBlock & 0xFC) + 3) * 16;
if (isBlockEmpty((traceCurBlock & 0xFC) + 3)) memcpy(traceCard + blockShift + 6, trailerAccessBytes, 4);
if (traceCurKey) {
num_to_bytes(key, 6, traceCard + blockShift + 10);
} else {
num_to_bytes(key, 6, traceCard + blockShift);
}
if (wantSaveToEmlFile) saveTraceCard();
if (traceCrypto1) {
crypto1_destroy(traceCrypto1);
}
// set cryptosystem state
traceCrypto1 = lfsr_recovery64(ks2, ks3);
// nt = crypto1_word(traceCrypto1, nt ^ uid, 1) ^ nt;
/* traceCrypto1 = crypto1_create(key); // key in lfsr
crypto1_word(traceCrypto1, nt ^ uid, 0);
crypto1_word(traceCrypto1, ar, 1);
crypto1_word(traceCrypto1, 0, 0);
crypto1_word(traceCrypto1, 0, 0);*/
return 0;
} else {
traceState = TRACE_ERROR;
return 1;
}
break;
default:
traceState = TRACE_ERROR;
return 1;
}
return 0;
}
