git.zerfleddert.de Git - proxmark3-svn/blob - armsrc/optimized_cipher.c

   1 /*****************************************************************************
   2  * WARNING
   3  *
   4  * THIS CODE IS CREATED FOR EXPERIMENTATION AND EDUCATIONAL USE ONLY.
   5  *
   6  * USAGE OF THIS CODE IN OTHER WAYS MAY INFRINGE UPON THE INTELLECTUAL
   7  * PROPERTY OF OTHER PARTIES, SUCH AS INSIDE SECURE AND HID GLOBAL,
   8  * AND MAY EXPOSE YOU TO AN INFRINGEMENT ACTION FROM THOSE PARTIES.
   9  *
  10  * THIS CODE SHOULD NEVER BE USED TO INFRINGE PATENTS OR INTELLECTUAL PROPERTY RIGHTS.
  11  *
  12  *****************************************************************************
  13  *
  14  * This file is part of loclass. It is a reconstructon of the cipher engine
  15  * used in iClass, and RFID techology.
  16  *
  17  * The implementation is based on the work performed by
  18  * Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
  19  * Milosch Meriac in the paper "Dismantling IClass".
  20  *
  21  * Copyright (C) 2014 Martin Holst Swende
  22  *
  23  * This is free software: you can redistribute it and/or modify
  24  * it under the terms of the GNU General Public License version 2 as published
  25  * by the Free Software Foundation.
  26  *
  27  * This file is distributed in the hope that it will be useful,
  28  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  29  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  30  * GNU General Public License for more details.
  31  *
  32  * You should have received a copy of the GNU General Public License
  33  * along with loclass.  If not, see <http://www.gnu.org/licenses/>.
  34  *
  35  *
  36  *
  37  ****************************************************************************/
  38
  39 /**
  40
  41   This file contains an optimized version of the MAC-calculation algorithm. Some measurements on
  42   a std laptop showed it runs in about 1/3 of the time:
  43
  44         Std: 0.428962
  45         Opt: 0.151609
  46
  47   Additionally, it is self-reliant, not requiring e.g. bitstreams from the cipherutils, thus can
  48   be easily dropped into a code base.
  49
  50   The optimizations have been performed in the following steps:
  51   * Parameters passed by reference instead of by value.
  52   * Iteration instead of recursion, un-nesting recursive loops into for-loops.
  53   * Handling of bytes instead of individual bits, for less shuffling and masking
  54   * Less creation of "objects", structs, and instead reuse of alloc:ed memory
  55   * Inlining some functions via #define:s
  56
  57   As a consequence, this implementation is less generic. Also, I haven't bothered documenting this.
  58   For a thorough documentation, check out the MAC-calculation within cipher.c instead.
  59
  60   -- MHS 2015
  61 **/
  62
  63 #include "optimized_cipher.h"
  64 #include <stdio.h>
  65 #include <stdlib.h>
  66 #include <string.h>
  67 #include <stdbool.h>
  68 #include <stdint.h>
  69 #include <time.h>
  70
  71 /**
  72 * Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
  73 * consisting of the following four components:
  74 *       1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
  75 *       2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
  76 *       3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
  77 *       4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
  78 **/
  79 typedef struct {
  80         uint8_t l;
  81         uint8_t r;
  82         uint8_t b;
  83         uint16_t t;
  84 } State;
  85
  86
  87 #define opt_T(s) (0x1 & ((s->t >> 15) ^ (s->t >> 14)^ (s->t >> 10)^ (s->t >> 8)^ (s->t >> 5)^ (s->t >> 4)^ (s->t >> 1)^ s->t))
  88
  89 #define opt_B(s) (((s->b >> 6) ^ (s->b >> 5) ^ (s->b >> 4) ^ (s->b)) & 0x1)
  90
  91 #define opt__select(x,y,r)  (4 & (((r & (r << 2)) >> 5) ^ ((r & ~(r << 2)) >> 4) ^ ( (r | r << 2) >> 3)))\
  92         |(2 & (((r | r << 2) >> 6) ^ ( (r | r << 2) >> 1) ^ (r >> 5) ^ r ^ ((x^y) << 1)))\
  93         |(1 & (((r & ~(r << 2)) >> 4) ^ ((r & (r << 2)) >> 3) ^ r ^ x))
  94
  95 /*
  96  * Some background on the expression above can be found here...
  97 uint8_t xopt__select(bool x, bool y, uint8_t r)
  98 {
  99         uint8_t r_ls2 = r << 2;
 100         uint8_t r_and_ls2 = r & r_ls2;
 101         uint8_t r_or_ls2  = r | r_ls2;
 102
 103         //r:      r0 r1 r2 r3 r4 r5 r6 r7
 104         //r_ls2:  r2 r3 r4 r5 r6 r7  0  0
 105         //                       z0
 106         //                          z1
 107
 108 //      uint8_t z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4); // <-- original
 109         uint8_t z0 = (r_and_ls2 >> 5) ^ ((r & ~r_ls2) >> 4) ^ ( r_or_ls2 >> 3);
 110
 111 //      uint8_t z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;  // <-- original
 112         uint8_t z1 = (r_or_ls2 >> 6) ^ ( r_or_ls2 >> 1) ^ (r >> 5) ^ r ^ ((x^y) << 1);
 113
 114 //      uint8_t z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x;  // <-- original
 115         uint8_t z2 = ((r & ~r_ls2) >> 4) ^ (r_and_ls2 >> 3) ^ r ^ x;
 116
 117         return (z0 & 4) | (z1 & 2) | (z2 & 1);
 118 }
 119 */
 120
 121 void opt_successor(uint8_t* k, State *s, bool y, State* successor)
 122 {
 123
 124         uint8_t Tt = 1 & opt_T(s);
 125
 126         successor->t = (s->t >> 1);
 127         successor->t |= (Tt ^ (s->r >> 7 & 0x1) ^ (s->r >> 3 & 0x1)) << 15;
 128
 129         successor->b = s->b >> 1;
 130         successor->b |= (opt_B(s) ^ (s->r & 0x1)) << 7;
 131
 132         successor->r = (k[opt__select(Tt,y,s->r)] ^ successor->b) + s->l ;
 133         successor->l = successor->r+s->r;
 134
 135 }
 136
 137 void opt_suc(uint8_t* k,State* s, uint8_t *in)
 138 {
 139         State x2;
 140         int i;
 141         uint8_t head = 0;
 142         for(i =0 ; i < 12 ; i++)
 143         {
 144                 head = 1 & (in[i] >> 7);
 145                 opt_successor(k,s,head,&x2);
 146
 147                 head = 1 & (in[i] >> 6);
 148                 opt_successor(k,&x2,head,s);
 149
 150                 head = 1 & (in[i] >> 5);
 151                 opt_successor(k,s,head,&x2);
 152
 153                 head = 1 & (in[i] >> 4);
 154                 opt_successor(k,&x2,head,s);
 155
 156                 head = 1 & (in[i] >> 3);
 157                 opt_successor(k,s,head,&x2);
 158
 159                 head = 1 & (in[i] >> 2);
 160                 opt_successor(k,&x2,head,s);
 161
 162                 head = 1 & (in[i] >> 1);
 163                 opt_successor(k,s,head,&x2);
 164
 165                 head = 1 & in[i];
 166                 opt_successor(k,&x2,head,s);
 167
 168         }
 169
 170 }
 171
 172 void opt_output(uint8_t* k,State* s,  uint8_t *buffer)
 173 {
 174         uint8_t times = 0;
 175         uint8_t bout = 0;
 176         State temp = {0,0,0,0};
 177         for( ; times < 4 ; times++)
 178         {
 179                 bout =0;
 180                 bout |= (s->r & 0x4) << 5;
 181                 opt_successor(k,s,0,&temp);
 182                 bout |= (temp.r & 0x4) << 4;
 183                 opt_successor(k,&temp,0,s);
 184                 bout |= (s->r & 0x4) << 3;
 185                 opt_successor(k,s,0,&temp);
 186                 bout |= (temp.r & 0x4) << 2;
 187                 opt_successor(k,&temp,0,s);
 188                 bout |= (s->r & 0x4) << 1;
 189                 opt_successor(k,s,0,&temp);
 190                 bout |= (temp.r & 0x4) ;
 191                 opt_successor(k,&temp,0,s);
 192                 bout |= (s->r & 0x4) >> 1;
 193                 opt_successor(k,s,0,&temp);
 194                 bout |= (temp.r & 0x4) >> 2;
 195                 opt_successor(k,&temp,0,s);
 196                 buffer[times] = bout;
 197         }
 198
 199 }
 200
 201 void opt_MAC(uint8_t* k, uint8_t* input, uint8_t* out)
 202 {
 203         State _init  =  {
 204                         ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
 205                         ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
 206                         0x4c, // b
 207                         0xE012 // t
 208                         };
 209
 210         opt_suc(k,&_init,input);
 211         //printf("\noutp ");
 212         opt_output(k,&_init, out);
 213 }
 214 uint8_t rev_byte(uint8_t b) {
 215         b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
 216         b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
 217         b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
 218    return b;
 219 }
 220 void opt_reverse_arraybytecpy(uint8_t* dest, uint8_t *src, size_t len)
 221 {
 222         uint8_t i;
 223         for( i =0; i< len ; i++)
 224                 dest[i] = rev_byte(src[i]);
 225 }
 226
 227 void opt_doMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
 228 {
 229         static uint8_t cc_nr[13];
 230         static uint8_t div_key[8];
 231
 232         opt_reverse_arraybytecpy(cc_nr, cc_nr_p,12);
 233         memcpy(div_key,div_key_p,8);
 234         uint8_t dest []= {0,0,0,0,0,0,0,0};
 235         opt_MAC(div_key,cc_nr, dest);
 236         //The output MAC must also be reversed
 237         opt_reverse_arraybytecpy(mac, dest,12);
 238         return;
 239 }