present/present.c

   1 /* present.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  * 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 buffer[10], tmp[2];
  76         uint8_t i;
  77         memcpy(buffer, key, 10);
  78         memcpy(&(ctx->k[0]), buffer+2, 8);
  79         for(i=1; i<32; ++i){
  80                 /* rotate buffer 19 right */
  81                 memcpy(tmp, buffer, 2);
  82                 memmove(buffer, buffer+2, 8);
  83                 memcpy(buffer+8, tmp, 2);
  84                  /* three shifts to do*/
  85                 tmp[1]=buffer[0];
  86                 *((uint64_t*)buffer)>>=3;
  87                 *((uint16_t*)(buffer+8))>>=3;
  88                 buffer[9] |= tmp[1]<<5;
  89                 buffer[7] |= tmp[0]<<5;
  90                 /* rotating done now substitution */
  91                 buffer[9] = (sbox(buffer[9])&0xF0) | ((buffer[9])&0x0F);
  92                 /* xor with round counter */
  93                 *((uint16_t*)(buffer+1)) ^= (uint16_t)i<<7;
  94                 memcpy(&(ctx->k[i]), buffer+2, 8);
  95         }
  96 }
  97
  98 void present_enc(void* buffer, present_ctx_t* ctx){
  99         uint8_t i,j,tmp[8];
 100         for(i=0; i<31; ++i){
 101                 *((uint64_t*)buffer) ^= ctx->k[i];
 102                  for(j=0; j<8; ++j){
 103                         tmp[j] = sbox(((uint8_t*)buffer)[j]);
 104                  }
 105                  p((uint16_t*)buffer, tmp);
 106         }
 107         *((uint64_t*)buffer) ^= ctx->k[31];
 108 }
 109
 110
 111 void present_dec(void* buffer, present_ctx_t* ctx){
 112         uint8_t j,tmp[8];
 113         int8_t i;
 114         *((uint64_t*)buffer) ^= ctx->k[31];
 115
 116         for(i=30; i>=0; --i){
 117                 p_inv(tmp, (uint8_t*)buffer);
 118                 for(j=0; j<8; ++j){
 119                         ((uint8_t*)buffer)[j] = sbox_inv(tmp[j]);
 120                 }
 121                 *((uint64_t*)buffer) ^= ctx->k[i];
 122         }
 123 }