present/present.c

   1 /* present.c */
   2 /*
   3     This file is part of the AVR-Crypto-Lib.
   4     Copyright (C) 2008  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  * present.c
  21  * a implementation of the PRESENT block-cipher
  22  * author: Daniel Otte
  23  * email:  daniel.otte@rub.de
  24  * license: GPLv3
  25  *
  26  * */
  27
  28 #include <string.h>
  29 #include <stdint.h>
  30 #include "present.h"
  31
  32 static uint8_t sbox(uint8_t b){
  33         uint8_t sb[]={0xC, 0x5, 0x6, 0xB,
  34                                   0x9, 0x0, 0xA, 0xD,
  35                                   0x3, 0xE, 0xF, 0x8,
  36                                   0x4, 0x7, 0x1, 0x2 };
  37         return (((sb[b>>4])<<4)|(sb[b&0xf]));
  38 }
  39
  40 static uint8_t sbox_inv(uint8_t b){
  41         uint8_t sb[]={0x5, 0xE, 0xF, 0x8,
  42                                   0xC, 0x1, 0x2, 0xD,
  43                                   0xB, 0x4, 0x6, 0x3,
  44                                   0x0, 0x7, 0x9, 0xA };
  45         return (((sb[b>>4])<<4)|(sb[b&0xf]));
  46 }
  47
  48 #define SHR_O(a) c=(a)&1; (a)>>=1;
  49 #define SHR_I(a) (a)=(c?0x8000:0x0000) | ((a)>>1);
  50
  51 static void p(uint16_t* o, uint8_t* i){
  52         uint8_t c;
  53         uint8_t m,n;
  54         for(m=0; m<8; ++m){
  55                 for(n=0; n<2; ++n){
  56                         SHR_O(i[m]);
  57                         SHR_I(o[0]);
  58                         SHR_O(i[m]);
  59                         SHR_I(o[1]);
  60                         SHR_O(i[m]);
  61                         SHR_I(o[2]);
  62                         SHR_O(i[m]);
  63                         SHR_I(o[3]);
  64                 }
  65         }
  66 }
  67
  68 static void p_inv(uint8_t* o, uint8_t* i){
  69         uint8_t tmp[8];
  70         p((uint16_t*)tmp, i);
  71         p((uint16_t*)o, tmp);
  72 }
  73
  74 void present_init(const uint8_t* key, uint8_t keysize_b, present_ctx_t* ctx){
  75         uint8_t tmp[2];
  76         union __attribute__((packed)) {
  77                 uint8_t  v8[10];
  78                 uint16_t v16[5];
  79                 uint64_t v64;
  80                 struct __attribute__((packed)) {
  81                         uint8_t padding;
  82                         union {
  83                                 uint64_t v64;
  84                                 uint16_t v16[4];
  85                         } y;
  86                 } x;
  87         } b;
  88         uint8_t i;
  89         memcpy(b.v8, key, 10);
  90         memcpy(&(ctx->k[0]), b.v8+2, 8);
  91         for(i=1; i<32; ++i){
  92                 /* rotate buffer 19 right */
  93                 memcpy(tmp, b.v8, 2);
  94                 memmove(b.v8, b.v8+2, 8);
  95                 memcpy(b.v8+8, tmp, 2);
  96                  /* three shifts to do*/
  97                 tmp[1]=b.v8[0];
  98                 b.v64 >>= 3;
  99                 b.v16[4] >>= 3;
 100                 b.v8[9] |= tmp[1]<<5;
 101                 b.v8[7] |= tmp[0]<<5;
 102                 /* rotating done now substitution */
 103                 b.v8[9] = (sbox(b.v8[9])&0xF0) | ((b.v8[9])&0x0F);
 104                 /* xor with round counter */
 105                 b.x.y.v16[0] ^= (uint16_t)i<<7;
 106                 memcpy(&(ctx->k[i]), b.v8+2, 8);
 107         }
 108 }
 109
 110 void present_enc(void* buffer, present_ctx_t* ctx){
 111         uint8_t i,j,tmp[8];
 112         for(i=0; i<31; ++i){
 113                 *((uint64_t*)buffer) ^= ctx->k[i];
 114                  for(j=0; j<8; ++j){
 115                         tmp[j] = sbox(((uint8_t*)buffer)[j]);
 116                  }
 117                  p((uint16_t*)buffer, tmp);
 118         }
 119         *((uint64_t*)buffer) ^= ctx->k[31];
 120 }
 121
 122
 123 void present_dec(void* buffer, present_ctx_t* ctx){
 124         uint8_t j,tmp[8];
 125         int8_t i;
 126         *((uint64_t*)buffer) ^= ctx->k[31];
 127
 128         for(i=30; i>=0; --i){
 129                 p_inv(tmp, (uint8_t*)buffer);
 130                 for(j=0; j<8; ++j){
 131                         ((uint8_t*)buffer)[j] = sbox_inv(tmp[j]);
 132                 }
 133                 *((uint64_t*)buffer) ^= ctx->k[i];
 134         }
 135 }