tools/mfkey/mfkey32.c

   1 #define __STDC_FORMAT_MACROS
   2 #include <inttypes.h>
   3 #include <stdbool.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include "crapto1/crapto1.h"
   7 #include "util_posix.h"
   8
   9 int main(int argc, char *argv[]) {
  10     struct Crypto1State *s, *t;
  11     uint64_t key;     // recovered key
  12     uint32_t uid;     // serial number
  13     uint32_t nt;      // tag challenge
  14     uint32_t nr0_enc; // first encrypted reader challenge
  15     uint32_t ar0_enc; // first encrypted reader response
  16     uint32_t nr1_enc; // second encrypted reader challenge
  17     uint32_t ar1_enc; // second encrypted reader response
  18     uint32_t ks2;     // keystream used to encrypt reader response
  19
  20     printf("MIFARE Classic key recovery - based on 32 bits of keystream\n");
  21     printf("Recover key from two 32-bit reader authentication answers only!\n\n");
  22
  23     if (argc < 7) {
  24         printf(" syntax: %s <uid> <nt> <nr_0> <ar_0> <nr_1> <ar_1>\n\n", argv[0]);
  25         return 1;
  26     }
  27
  28     sscanf(argv[1], "%x", &uid);
  29     sscanf(argv[2], "%x", &nt);
  30     sscanf(argv[3], "%x", &nr0_enc);
  31     sscanf(argv[4], "%x", &ar0_enc);
  32     sscanf(argv[5], "%x", &nr1_enc);
  33     sscanf(argv[6], "%x", &ar1_enc);
  34
  35     printf("Recovering key for:\n");
  36     printf("    uid: %08x\n", uid);
  37     printf("     nt: %08x\n", nt);
  38     printf(" {nr_0}: %08x\n", nr0_enc);
  39     printf(" {ar_0}: %08x\n", ar0_enc);
  40     printf(" {nr_1}: %08x\n", nr1_enc);
  41     printf(" {ar_1}: %08x\n", ar1_enc);
  42
  43     // Generate lfsr succesors of the tag challenge
  44     printf("\nLFSR succesors of the tag challenge:\n");
  45     uint32_t p64 = prng_successor(nt, 64);
  46     printf("  nt': %08x\n", p64);
  47     printf(" nt'': %08x\n", prng_successor(p64, 32));
  48
  49     // Extract the keystream from the messages
  50     printf("\nKeystream used to generate {ar} and {at}:\n");
  51     ks2 = ar0_enc ^ p64;
  52     printf("  ks2: %08x\n", ks2);
  53
  54     s = lfsr_recovery32(ar0_enc ^ p64, 0);
  55
  56     for (t = s; t->odd | t->even; ++t) {
  57         lfsr_rollback_word(t, 0, 0);
  58         lfsr_rollback_word(t, nr0_enc, 1);
  59         lfsr_rollback_word(t, uid ^ nt, 0);
  60         crypto1_get_lfsr(t, &key);
  61         crypto1_word(t, uid ^ nt, 0);
  62         crypto1_word(t, nr1_enc, 1);
  63         if (ar1_enc == (crypto1_word(t, 0, 0) ^ p64)) {
  64             printf("\nFound Key: [%012" PRIx64 "]\n\n", key);
  65             break;
  66         }
  67     }
  68     free(s);
  69     return 0;
  70 }