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 }