Merge pull request #113 from pwpiwi/iso14443b_fix
[proxmark3-svn] / 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 #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))
73
74 #define opt_B(s) (((s->b >> 6) ^ (s->b >> 5) ^ (s->b >> 4) ^ (s->b)) & 0x1)
75
76 #define opt__select(x,y,r) (4 & (((r & (r << 2)) >> 5) ^ ((r & ~(r << 2)) >> 4) ^ ( (r | r << 2) >> 3)))\
77 |(2 & (((r | r << 2) >> 6) ^ ( (r | r << 2) >> 1) ^ (r >> 5) ^ r ^ ((x^y) << 1)))\
78 |(1 & (((r & ~(r << 2)) >> 4) ^ ((r & (r << 2)) >> 3) ^ r ^ x))
79
80 /*
81 * Some background on the expression above can be found here...
82 uint8_t xopt__select(bool x, bool y, uint8_t r)
83 {
84 uint8_t r_ls2 = r << 2;
85 uint8_t r_and_ls2 = r & r_ls2;
86 uint8_t r_or_ls2 = r | r_ls2;
87
88 //r: r0 r1 r2 r3 r4 r5 r6 r7
89 //r_ls2: r2 r3 r4 r5 r6 r7 0 0
90 // z0
91 // z1
92
93 // uint8_t z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4); // <-- original
94 uint8_t z0 = (r_and_ls2 >> 5) ^ ((r & ~r_ls2) >> 4) ^ ( r_or_ls2 >> 3);
95
96 // uint8_t z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y; // <-- original
97 uint8_t z1 = (r_or_ls2 >> 6) ^ ( r_or_ls2 >> 1) ^ (r >> 5) ^ r ^ ((x^y) << 1);
98
99 // uint8_t z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x; // <-- original
100 uint8_t z2 = ((r & ~r_ls2) >> 4) ^ (r_and_ls2 >> 3) ^ r ^ x;
101
102 return (z0 & 4) | (z1 & 2) | (z2 & 1);
103 }
104 */
105
106 void opt_successor(const uint8_t* k, State *s, bool y, State* successor)
107 {
108
109 uint8_t Tt = 1 & opt_T(s);
110
111 successor->t = (s->t >> 1);
112 successor->t |= (Tt ^ (s->r >> 7 & 0x1) ^ (s->r >> 3 & 0x1)) << 15;
113
114 successor->b = s->b >> 1;
115 successor->b |= (opt_B(s) ^ (s->r & 0x1)) << 7;
116
117 successor->r = (k[opt__select(Tt,y,s->r)] ^ successor->b) + s->l ;
118 successor->l = successor->r+s->r;
119
120 }
121
122 void opt_suc(const uint8_t* k,State* s, uint8_t *in, uint8_t length, bool add32Zeroes)
123 {
124 State x2;
125 int i;
126 uint8_t head = 0;
127 for(i =0 ; i < length ; i++)
128 {
129 head = 1 & (in[i] >> 7);
130 opt_successor(k,s,head,&x2);
131
132 head = 1 & (in[i] >> 6);
133 opt_successor(k,&x2,head,s);
134
135 head = 1 & (in[i] >> 5);
136 opt_successor(k,s,head,&x2);
137
138 head = 1 & (in[i] >> 4);
139 opt_successor(k,&x2,head,s);
140
141 head = 1 & (in[i] >> 3);
142 opt_successor(k,s,head,&x2);
143
144 head = 1 & (in[i] >> 2);
145 opt_successor(k,&x2,head,s);
146
147 head = 1 & (in[i] >> 1);
148 opt_successor(k,s,head,&x2);
149
150 head = 1 & in[i];
151 opt_successor(k,&x2,head,s);
152
153 }
154 //For tag MAC, an additional 32 zeroes
155 if(add32Zeroes)
156 for(i =0 ; i < 16 ; i++)
157 {
158 opt_successor(k,s,0,&x2);
159 opt_successor(k,&x2,0,s);
160 }
161 }
162
163 void opt_output(const uint8_t* k,State* s, uint8_t *buffer)
164 {
165 uint8_t times = 0;
166 uint8_t bout = 0;
167 State temp = {0,0,0,0};
168 for( ; times < 4 ; times++)
169 {
170 bout =0;
171 bout |= (s->r & 0x4) << 5;
172 opt_successor(k,s,0,&temp);
173 bout |= (temp.r & 0x4) << 4;
174 opt_successor(k,&temp,0,s);
175 bout |= (s->r & 0x4) << 3;
176 opt_successor(k,s,0,&temp);
177 bout |= (temp.r & 0x4) << 2;
178 opt_successor(k,&temp,0,s);
179 bout |= (s->r & 0x4) << 1;
180 opt_successor(k,s,0,&temp);
181 bout |= (temp.r & 0x4) ;
182 opt_successor(k,&temp,0,s);
183 bout |= (s->r & 0x4) >> 1;
184 opt_successor(k,s,0,&temp);
185 bout |= (temp.r & 0x4) >> 2;
186 opt_successor(k,&temp,0,s);
187 buffer[times] = bout;
188 }
189
190 }
191
192 void opt_MAC(uint8_t* k, uint8_t* input, uint8_t* out)
193 {
194 State _init = {
195 ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
196 ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
197 0x4c, // b
198 0xE012 // t
199 };
200
201 opt_suc(k,&_init,input,12, false);
202 //printf("\noutp ");
203 opt_output(k,&_init, out);
204 }
205 uint8_t rev_byte(uint8_t b) {
206 b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
207 b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
208 b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
209 return b;
210 }
211 void opt_reverse_arraybytecpy(uint8_t* dest, uint8_t *src, size_t len)
212 {
213 uint8_t i;
214 for( i =0; i< len ; i++)
215 dest[i] = rev_byte(src[i]);
216 }
217
218 void opt_doReaderMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
219 {
220 static uint8_t cc_nr[12];
221
222 opt_reverse_arraybytecpy(cc_nr, cc_nr_p,12);
223 uint8_t dest []= {0,0,0,0,0,0,0,0};
224 opt_MAC(div_key_p,cc_nr, dest);
225 //The output MAC must also be reversed
226 opt_reverse_arraybytecpy(mac, dest,4);
227 return;
228 }
229 void opt_doTagMAC(uint8_t *cc_p, const uint8_t *div_key_p, uint8_t mac[4])
230 {
231 static uint8_t cc_nr[8+4+4];
232 opt_reverse_arraybytecpy(cc_nr, cc_p,12);
233 State _init = {
234 ((div_key_p[0] ^ 0x4c) + 0xEC) & 0xFF,// l
235 ((div_key_p[0] ^ 0x4c) + 0x21) & 0xFF,// r
236 0x4c, // b
237 0xE012 // t
238 };
239 opt_suc(div_key_p,&_init,cc_nr, 12,true);
240 uint8_t dest []= {0,0,0,0};
241 opt_output(div_key_p,&_init, dest);
242 //The output MAC must also be reversed
243 opt_reverse_arraybytecpy(mac, dest,4);
244 return;
245
246 }
247 /**
248 * The tag MAC can be divided (both can, but no point in dividing the reader mac) into
249 * two functions, since the first 8 bytes are known, we can pre-calculate the state
250 * reached after feeding CC to the cipher.
251 * @param cc_p
252 * @param div_key_p
253 * @return the cipher state
254 */
255 State opt_doTagMAC_1(uint8_t *cc_p, const uint8_t *div_key_p)
256 {
257 static uint8_t cc_nr[8];
258 opt_reverse_arraybytecpy(cc_nr, cc_p,8);
259 State _init = {
260 ((div_key_p[0] ^ 0x4c) + 0xEC) & 0xFF,// l
261 ((div_key_p[0] ^ 0x4c) + 0x21) & 0xFF,// r
262 0x4c, // b
263 0xE012 // t
264 };
265 opt_suc(div_key_p,&_init,cc_nr, 8,false);
266 return _init;
267 }
268 /**
269 * The second part of the tag MAC calculation, since the CC is already calculated into the state,
270 * this function is fed only the NR, and internally feeds the remaining 32 0-bits to generate the tag
271 * MAC response.
272 * @param _init - precalculated cipher state
273 * @param nr - the reader challenge
274 * @param mac - where to store the MAC
275 * @param div_key_p - the key to use
276 */
277 void opt_doTagMAC_2(State _init, uint8_t* nr, uint8_t mac[4], const uint8_t* div_key_p)
278 {
279 static uint8_t _nr [4];
280 opt_reverse_arraybytecpy(_nr, nr, 4);
281 opt_suc(div_key_p,&_init,_nr, 4, true);
282 //opt_suc(div_key_p,&_init,nr, 4, false);
283 uint8_t dest []= {0,0,0,0};
284 opt_output(div_key_p,&_init, dest);
285 //The output MAC must also be reversed
286 opt_reverse_arraybytecpy(mac, dest,4);
287 return;
288 }
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