From a78238349cc481d241da6674801a2cb7ee58cdea Mon Sep 17 00:00:00 2001
From: Pavel Zhovner <pavel@zhovner.com>
Date: Wed, 9 Mar 2016 02:41:20 +0300
Subject: [PATCH] Optional decryption of communication using keystream

---
 tools/mfkey/mfkey64.c | 69 +++++++++++++++++++++++++++++++++----------
 1 file changed, 54 insertions(+), 15 deletions(-)

diff --git a/tools/mfkey/mfkey64.c b/tools/mfkey/mfkey64.c
index 448cb2ac..eeb9bb65 100755
--- a/tools/mfkey/mfkey64.c
+++ b/tools/mfkey/mfkey64.c
@@ -6,6 +6,7 @@
 // Test-file: test2.c
 #include "crapto1.h"
 #include <stdio.h>
+#include <string.h>
 
 int main (int argc, char *argv[]) {
   struct Crypto1State *revstate;
@@ -21,32 +22,50 @@ int main (int argc, char *argv[]) {
   printf("MIFARE Classic key recovery - based 64 bits of keystream\n");
   printf("Recover key from only one complete authentication!\n\n");
 
-  if (argc < 6) {
-    printf(" syntax: %s <uid> <nt> <{nr}> <{ar}> <{at}>\n\n",argv[0]);
+  if (argc < 6 ) {
+    printf(" syntax: %s <uid> <nt> <{nr}> <{ar}> <{at}> <[enc]> [enc...]\n\n", argv[0]);
     return 1;
   }
 
-  sscanf(argv[1],"%x",&uid);
-  sscanf(argv[2],"%x",&nt);
-  sscanf(argv[3],"%x",&nr_enc);
-  sscanf(argv[4],"%x",&ar_enc);
-  sscanf(argv[5],"%x",&at_enc);
+  int encc = argc - 6;
+  int enclen[encc];
+  uint8_t enc[encc][120]; 
 
+  sscanf(argv[1], "%x", &uid);
+  sscanf(argv[2], "%x", &nt);
+  sscanf(argv[3], "%x", &nr_enc);
+  sscanf(argv[4], "%x", &ar_enc);
+  sscanf(argv[5], "%x", &at_enc);
+  for (int i = 0; i < encc; i++) {
+    enclen[i] = strlen(argv[i + 6]) / 2;
+    for (int i2 = 0; i2 < enclen[i]; i2++) {
+      sscanf(argv[i+6] + i2*2,"%2x", (uint8_t*)&enc[i][i2]);
+    }
+  }
   printf("Recovering key for:\n");
-  printf("  uid: %08x\n",uid);
-  printf("   nt: %08x\n",nt);
-  printf(" {nr}: %08x\n",nr_enc);
-  printf(" {ar}: %08x\n",ar_enc);
-  printf(" {at}: %08x\n",at_enc);
 
-/*	
+  printf("  uid: %08x\n", uid);
+  printf("   nt: %08x\n", nt);
+  printf(" {nr}: %08x\n", nr_enc);
+  printf(" {ar}: %08x\n", ar_enc);
+  printf(" {at}: %08x\n", at_enc);
+  for (int i = 0; i < encc; i++) {
+      printf("{enc%d}: ", i);
+      for (int i2 = 0; i2 < enclen[i]; i2++) {
+          printf("%02x", enc[i][i2]);
+      }
+      printf("\n");
+  }
+
+
+  /*  
   uint32_t uid                = 0x9c599b32;
   uint32_t tag_challenge      = 0x82a4166c;
   uint32_t nr_enc             = 0xa1e458ce;
   uint32_t reader_response    = 0x6eea41e0;
   uint32_t tag_response       = 0x5cadf439;
 */
-	// Generate lfsr succesors of the tag challenge
+  // Generate lfsr succesors of the tag challenge
   printf("\nLFSR succesors of the tag challenge:\n");
   printf("  nt': %08x\n",prng_successor(nt, 64));
   printf(" nt'': %08x\n",prng_successor(nt, 96));
@@ -59,6 +78,26 @@ int main (int argc, char *argv[]) {
   printf("  ks3: %08x\n",ks3);
 
   revstate = lfsr_recovery64(ks2, ks3);
+
+  // Decrypting communication using keystream if presented
+  if (argc > 6 ) {
+  printf("\nDecrypted communication:\n");
+  uint8_t ks4; 
+  int rollb = 0;
+  for (int i = 0; i < encc; i++) {
+    printf("{dec%d}: ", i);
+    for (int i2 = 0; i2 < enclen[i]; i2++) {  
+      ks4 = crypto1_byte(revstate, 0, 0);
+      printf("%02x", ks4 ^ enc[i][i2]);
+      rollb += 1;
+    }
+    printf("\n");
+  }
+  for (int i = 0; i < rollb; i++) {
+    lfsr_rollback_byte(revstate, 0, 0);
+    }
+  }
+  
   lfsr_rollback_word(revstate, 0, 0);
   lfsr_rollback_word(revstate, 0, 0);
   lfsr_rollback_word(revstate, nr_enc, 1);
@@ -68,4 +107,4 @@ int main (int argc, char *argv[]) {
   crypto1_destroy(revstate);
 
   return 0;
-}
+}
\ No newline at end of file
-- 
2.39.2