tools/mfc/card_reader/mfkey32nested.c

   1 //  Doegox, 2024, cf https://eprint.iacr.org/2024/1275 for more info
   2
   3 #include <inttypes.h>
   4 #include <stdbool.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include "crapto1/crapto1.h"
   8 #include "util_posix.h"
   9
  10 int main(int argc, char *argv[]) {
  11     struct Crypto1State *s, *t;
  12     uint64_t key;     // recovered key
  13     uint32_t uid;     // serial number
  14     uint32_t nt;      // tag nonce
  15     uint32_t nt_enc;  // encrypted tag nonce
  16     uint32_t nr_enc;  // encrypted reader nonce
  17     uint32_t ar;      // reader response
  18     uint32_t ar_enc;  // encrypted reader response
  19     uint32_t ks0;     // keystream used to encrypt tag nonce
  20     uint32_t ks2;     // keystream used to encrypt reader response
  21
  22     printf("MIFARE Classic key recovery - known nT scenario\n");
  23     printf("Recover key from one reader authentication answer only\n");
  24
  25     if (argc != 6) {
  26         printf("syntax: %s <uid> <nt> <{nt}> <{nr}> <{ar}>\n\n", argv[0]);
  27         return 1;
  28     }
  29
  30     sscanf(argv[1], "%x", &uid);
  31     sscanf(argv[2], "%x", &nt);
  32     sscanf(argv[3], "%x", &nt_enc);
  33     sscanf(argv[4], "%x", &nr_enc);
  34     sscanf(argv[5], "%x", &ar_enc);
  35
  36     printf("Recovering key for:\n");
  37     printf("    uid: %08x\n", uid);
  38     printf("     nt: %08x\n", nt);
  39     printf("   {nt}: %08x\n", nt_enc);
  40     printf("   {nr}: %08x\n", nr_enc);
  41     printf("   {ar}: %08x\n", ar_enc);
  42
  43     printf("\nLFSR successor of the tag challenge:\n");
  44     ar = prng_successor(nt, 64);
  45     printf("     ar: %08x\n", ar);
  46
  47     printf("\nKeystream used to generate {nt}:\n");
  48     ks0 = nt_enc ^ nt;
  49     printf("    ks0: %08x\n", ks0);
  50     printf("\nKeystream used to generate {ar}:\n");
  51     ks2 = ar_enc ^ ar;
  52     printf("    ks2: %08x\n", ks2);
  53
  54     s = lfsr_recovery32(ks0, uid ^ nt);
  55
  56     for (t = s; t->odd | t->even; ++t) {
  57         crypto1_word(t, nr_enc, 1);
  58         if (ks2 == crypto1_word(t, 0, 0)) {
  59             lfsr_rollback_word(t, 0, 0);
  60             lfsr_rollback_word(t, nr_enc, 1);
  61             lfsr_rollback_word(t, uid ^ nt, 0);
  62             crypto1_get_lfsr(t, &key);
  63             printf("\nFound Key: [%012" PRIx64 "]\n\n", key);
  64             break;
  65         }
  66     }
  67     free(s);
  68     return 0;
  69 }