Fixed issue #43 on github
[proxmark3-svn] / client / loclass / cipher.c
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1/*****************************************************************************
2 * This file is part of iClassCipher. It is a reconstructon of the cipher engine
3 * used in iClass, and RFID techology.
4 *
5 * The implementation is based on the work performed by
6 * Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
7 * Milosch Meriac in the paper "Dismantling IClass".
8 *
9 * Copyright (C) 2014 Martin Holst Swende
10 *
11 * This is free software: you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as published
13 * by the Free Software Foundation.
14 *
15 * This file is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with IClassCipher. If not, see <http://www.gnu.org/licenses/>.
22 ****************************************************************************/
23
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24#include "cipher.h"
25#include "cipherutils.h"
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26#include <stdio.h>
27#include <stdlib.h>
28#include <string.h>
29#include <stdbool.h>
30#include <stdint.h>
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31#include <time.h>
32#include "fileutils.h"
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33uint8_t keytable[] = { 0,0,0,0,0,0,0,0};
34
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35/**
36* Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
37* consisting of the following four components:
38* 1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
39* 2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
40* 3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
41* 4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
42**/
43typedef struct {
44 uint8_t l;
45 uint8_t r;
46 uint8_t b;
47 uint16_t t;
48} State;
49
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50/**
51* Definition 2. The feedback function for the top register T : F 16/2 → F 2
52* is defined as
53* T (x 0 x 1 . . . . . . x 15 ) = x 0 ⊕ x 1 ⊕ x 5 ⊕ x 7 ⊕ x 10 ⊕ x 11 ⊕ x 14 ⊕ x 15 .
54**/
55bool T(State state)
56{
57 bool x0 = state.t & 0x8000;
58 bool x1 = state.t & 0x4000;
59 bool x5 = state.t & 0x0400;
60 bool x7 = state.t & 0x0100;
61 bool x10 = state.t & 0x0020;
62 bool x11 = state.t & 0x0010;
63 bool x14 = state.t & 0x0002;
64 bool x15 = state.t & 0x0001;
65 return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
66}
67/**
68* Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
69* B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
70**/
71bool B(State state)
72{
73 bool x1 = state.b & 0x40;
74 bool x2 = state.b & 0x20;
75 bool x3 = state.b & 0x10;
76 bool x7 = state.b & 0x01;
77
78 return x1 ^ x2 ^ x3 ^ x7;
79
80}
81
82
83/**
84* Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
85* F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
86* z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
87* z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
88* z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
89**/
90uint8_t _select(bool x, bool y, uint8_t r)
91{
92 bool r0 = r >> 7 & 0x1;
93 bool r1 = r >> 6 & 0x1;
94 bool r2 = r >> 5 & 0x1;
95 bool r3 = r >> 4 & 0x1;
96 bool r4 = r >> 3 & 0x1;
97 bool r5 = r >> 2 & 0x1;
98 bool r6 = r >> 1 & 0x1;
99 bool r7 = r & 0x1;
100
101 bool z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4);
102 bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
103 bool z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x;
104
105 // The three bitz z0.. z1 are packed into a uint8_t:
106 // 00000ZZZ
107 //Return value is a uint8_t
108 uint8_t retval = 0;
109 retval |= (z0 << 2) & 4;
110 retval |= (z1 << 1) & 2;
111 retval |= z2 & 1;
112
113 // Return value 0 <= retval <= 7
114 return retval;
115}
116
117/**
118* Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
119* be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
120* l ′ , r ′ , t ′ , b ′ is defined as
121* t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
122* b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
123*
124* @param s - state
125* @param k - array containing 8 bytes
126**/
127State successor(uint8_t* k, State s, bool y)
128{
129 bool r0 = s.r >> 7 & 0x1;
130 bool r4 = s.r >> 3 & 0x1;
131 bool r7 = s.r & 0x1;
132
133 State successor = {0,0,0,0};
134
135 successor.t = s.t >> 1;
136 successor.t |= (T(s) ^ r0 ^ r4) << 15;
137
138 successor.b = s.b >> 1;
139 successor.b |= (B(s) ^ r7) << 7;
140
141 bool Tt = T(s);
142
143 successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
144 successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
145
146 return successor;
147}
148/**
149* We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
150* an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
151* to multiple bit input x ∈ F n 2 which we define as
152* @param k - array containing 8 bytes
153**/
154State suc(uint8_t* k,State s, BitstreamIn *bitstream)
155{
156 if(bitsLeft(bitstream) == 0)
157 {
158 return s;
159 }
160 bool lastbit = tailBit(bitstream);
161 return successor(k,suc(k,s,bitstream), lastbit);
162}
163
164/**
165* Definition 5 (Output). Define the function output which takes an internal
166* state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
167* on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
168* output(k, s, ǫ) = ǫ
169* output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
170* where s ′ = suc(k, s, x 0 ).
171**/
172void output(uint8_t* k,State s, BitstreamIn* in, BitstreamOut* out)
173{
174 if(bitsLeft(in) == 0)
175 {
176 return;
177 }
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178 pushBit(out,(s.r >> 2) & 1);
179 //Remove first bit
180 uint8_t x0 = headBit(in);
181 State ss = successor(k,s,x0);
182 output(k,ss,in, out);
183}
184
185/**
186* Definition 6 (Initial state). Define the function init which takes as input a
187* key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
188**/
189
190State init(uint8_t* k)
191{
192 State s = {
193 ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
194 ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
195 0x4c, // b
196 0xE012 // t
197 };
198 return s;
199}
200void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
201{
202 uint8_t zeroes_32[] = {0,0,0,0};
203 BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
204 State initState = suc(k,init(k),&input);
205 output(k,initState,&input_32_zeroes,&out);
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206}
207
aa41c605 208void doMAC(uint8_t *cc_nr_p, int length, uint8_t *div_key_p, uint8_t mac[4])
a66fca86 209{
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210 uint8_t *cc_nr;
211 uint8_t div_key[8];
212 cc_nr=(uint8_t*)malloc(length+1);
213 memcpy(cc_nr,cc_nr_p,length);
214 memcpy(div_key,div_key_p,8);
aa41c605 215
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216 reverse_arraybytes(cc_nr,length);
217 BitstreamIn bitstream = {cc_nr,length * 8,0};
218 uint8_t dest []= {0,0,0,0,0,0,0,0};
219 BitstreamOut out = { dest, sizeof(dest)*8, 0 };
220 MAC(div_key,bitstream, out);
221 //The output MAC must also be reversed
222 reverse_arraybytes(dest, sizeof(dest));
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223 memcpy(mac, dest, 4);
224 //printf("Calculated_MAC\t%02x%02x%02x%02x\n", dest[0],dest[1],dest[2],dest[3]);
74a38802 225 free(cc_nr);
aa41c605 226 return;
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227}
228
229int testMAC()
230{
3ad48540 231 prnlog("[+] Testing MAC calculation...");
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232
233 //From the "dismantling.IClass" paper:
234 uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
a66fca86 235 //From the paper
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236 uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
237 uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA};
a66fca86 238
3ad48540 239 uint8_t calculated_mac[4] = {0};
aa41c605 240 doMAC(cc_nr, 12,div_key, calculated_mac);
a66fca86 241
3ad48540 242 if(memcmp(calculated_mac, correct_MAC,4) == 0)
a66fca86 243 {
3ad48540 244 prnlog("[+] MAC calculation OK!");
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245
246 }else
247 {
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248 prnlog("[+] FAILED: MAC calculation failed:");
249 printarr(" Calculated_MAC", calculated_mac, 4);
250 printarr(" Correct_MAC ", correct_MAC, 4);
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251 return 1;
252 }
3ad48540 253
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254 return 0;
255}
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