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some minor improvments and bug fixes
[avr-crypto-lib.git] / cscipher / cscipher_small.c
1 /* cscipher_small_core.c */
2 /*
3     This file is part of the ARM-Crypto-Lib.
4     Copyright (C) 2006-2010 Daniel Otte (daniel.otte@rub.de)
5
6     This program is free software: you can redistribute it and/or modify
7     it under the terms of the GNU General Public License as published by
8     the Free Software Foundation, either version 3 of the License, or
9     (at your option) any later version.
10
11     This program is distributed in the hope that it will be useful,
12     but WITHOUT ANY WARRANTY; without even the implied warranty of
13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14     GNU General Public License for more details.
15
16     You should have received a copy of the GNU General Public License
17     along with this program.  If not, see <http://www.gnu.org/licenses/>.
18 */
19
20 #include <stdint.h>
21 #include <avr/pgmspace.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include "memxor.h"
25 #include "cscipher.h"
26
27 #define DEBUG 0
28
29 #if DEBUG
30 #include "cli.h"
31 #endif
32
33 #define ROTL(a) (((a)<<1)|((a)>>7))
34
35 #ifndef SBOX_PROG
36 #define SBOX_PROG 0
37 #endif
38
39 #if SBOX_PROG
40 static const uint8_t fg_table[] PROGMEM = {
41                 0xfa, 0xd6, 0xb0, 0xb2, 0x7b, 0x5e, 0x71, 0x78,
42                 0xed, 0xd4, 0xa5, 0xb3, 0xef, 0xdc, 0xe7, 0xf9
43 };
44
45 static
46 uint8_t p(uint8_t a){
47         a ^= pgm_read_byte(fg_table+(a&0xf))&0xf0;
48         a ^= pgm_read_byte(fg_table+(a>>4)) &0x0f;
49         a ^= pgm_read_byte(fg_table+(a&0xf))&0xf0;
50         return a;
51 }
52 #define P(a) p(a)
53
54 #else
55
56 #include "cscipher_sbox.h"
57 #define P(a) pgm_read_byte(cscipher_sbox+(a))
58 #endif
59
60 static const uint8_t round_const[] PROGMEM = {
61         0xb7, 0xe1, 0x51, 0x62, 0x8a, 0xed, 0x2a, 0x6a,
62         0xbf, 0x71, 0x58, 0x80, 0x9c, 0xf4, 0xf3, 0xc7 };
63
64 static const uint8_t ks_const[] PROGMEM = {
65         0x29,0x0d,0x61,0x40,0x9c,0xeb,0x9e,0x8f,
66         0x1f,0x85,0x5f,0x58,0x5b,0x01,0x39,0x86,
67         0x97,0x2e,0xd7,0xd6,0x35,0xae,0x17,0x16,
68         0x21,0xb6,0x69,0x4e,0xa5,0x72,0x87,0x08,
69         0x3c,0x18,0xe6,0xe7,0xfa,0xad,0xb8,0x89,
70         0xb7,0x00,0xf7,0x6f,0x73,0x84,0x11,0x63,
71         0x3f,0x96,0x7f,0x6e,0xbf,0x14,0x9d,0xac,
72         0xa4,0x0e,0x7e,0xf6,0x20,0x4a,0x62,0x30,
73         0x03,0xc5,0x4b,0x5a,0x46,0xa3,0x44,0x65
74 };
75
76 static uint16_t m(uint16_t a){
77         uint8_t xl, xr, yl, yr;
78         uint16_t ret;
79         xr = a>>8;
80         xl = a&0xff;
81         yl = (ROTL(xl)&0x55)^xl^xr;
82         yr = ROTL(xl)^xr;
83         ret = (P(yr)<<8)|P(yl);
84         return ret;
85 }
86
87 static uint16_t m_inv(uint16_t a){
88         uint8_t xl, xr;
89         xr = P(a>>8);
90         xl = P(a&0xff);
91         xl ^= xr;
92         xl ^= (ROTL(xl)&0xaa);
93         xr ^= ROTL(xl);
94         return (xr<<8)|xl;
95 }
96
97
98 void cscipher_enc(void* buffer, const cscipher_ctx_t* ctx){
99         uint8_t i,j,k;
100         uint8_t tmp[8];
101         for(i=0; i<8; ++i){
102 #if DEBUG
103                 cli_putstr_P(PSTR("\r\nDBG: round "));
104                 cli_hexdump(&i, 1);
105                 cli_putstr_P(PSTR(" buffer:"));
106                 cli_hexdump(buffer, 8);
107 #endif
108                 for(j=0; j<3; ++j){
109                         if(j==0){
110                                 memxor(buffer, ctx->keys[i], 8);
111                         }else{
112                                 memxor_P(buffer, round_const+((j==1)?0:8), 8);
113                         }
114                         for(k=0; k<4; ++k){
115                                 ((uint16_t*)tmp)[k] = m(((uint16_t*)buffer)[k]);
116                         }
117                         for(k=0; k<4; ++k){
118                                 ((uint8_t*)buffer)[k]   = tmp[2*k];
119                                 ((uint8_t*)buffer)[k+4] = tmp[2*k+1];
120                         }
121                 }
122         }
123         memxor(buffer, ctx->keys[8], 8);
124 }
125
126 void cscipher_dec(void* buffer, const cscipher_ctx_t* ctx){
127         uint8_t i=7,j,k;
128         uint8_t tmp[8];
129         memxor(buffer, ctx->keys[8], 8);
130         do{
131                 for(j=0; j<3; ++j){
132                         for(k=0; k<4; ++k){
133                                 tmp[2*k]   = ((uint8_t*)buffer)[k];
134                                 tmp[2*k+1] = ((uint8_t*)buffer)[4+k];
135                         }
136                         for(k=0; k<4; ++k){
137                                 ((uint16_t*)buffer)[k] = m_inv(((uint16_t*)tmp)[k]);
138                         }
139                         if(j==2){
140                                 memxor(buffer, ctx->keys[i], 8);
141                         }else{
142                                 memxor_P(buffer, round_const+((j==1)?0:8), 8);
143                         }
144
145                 }
146         }while(i--);
147 }
148
149 void cscipher_init(const void* key, cscipher_ctx_t* ctx){
150         uint8_t tmp_key[16], tmp[8];
151         uint8_t i,j,k,t=0;
152         memcpy(tmp_key, key, 16);
153         for(i=0; i<9; ++i){
154 #if DEBUG
155                 cli_putstr_P(PSTR("\r\nDBG: round "));
156                 cli_hexdump(&i, 1);
157                 cli_putstr_P(PSTR(" key state:"));
158                 cli_hexdump(tmp_key, 16);
159 #endif
160                 memcpy(tmp, tmp_key+(((i&1)==0)?0:8), 8);
161                 memxor_P(tmp, ks_const+8*i, 8);
162                 for(j=0; j<8; ++j){
163                         tmp[j] = P(tmp[j]);
164                 }
165                 for(j=0; j<8; ++j){
166                         for(k=0; k<8; ++k){
167                                 t<<=1;
168                                 t |= tmp[k]>>7;
169                                 tmp[k]<<=1;
170                         }
171                         tmp_key[j+(((i&1)==0)?8:0)] ^= t;
172                 }
173                 memcpy(ctx->keys[i], tmp_key+(((i&1)==0)?8:0), 8);
174         }
175 }