shabea.c

   1 /**
   2  * \file        shabea.c
   3  * \author      Daniel Otte
   4  * \date        2007-06-07
   5  * \brief       SHABEA - a SHA Based Encryption Algorithm implementation
   6  * \par License
   7  * GPL
   8  *
   9  * SHABEAn-r where n is the blocksize and r the number of round used
  10  *
  11  *
  12  */
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include "sha256.h"
  16
  17 #include "config.h"
  18 #include "uart.h"
  19 #include "debug.h"
  20 /*
  21  *
  22  */
  23 void memxor(uint8_t * dest, uint8_t * src, uint8_t length){
  24         while(length--){
  25                 *dest++ ^= *src++;
  26         }
  27 }
  28
  29 /*
  30  * SHABEA256-n
  31  */
  32
  33 #define BLOCKSIZE 256
  34 #define BLOCKSIZEB (BLOCKSIZE/8)
  35 #define HALFSIZEB  (BLOCKSIZEB/2)
  36 #define HALFSIZE (BLOCKSIZE/2)
  37
  38 #define L ((uint8_t*)block+ 0)
  39 #define R ((uint8_t*)block+16)
  40 void shabea256(void * block, void * key, uint16_t keysize, uint8_t enc, uint8_t rounds){
  41         int8_t r;               /**/
  42         uint8_t tb[HALFSIZEB+2+(keysize+7)/8];  /**/
  43         uint16_t kbs;   /* bytes used for the key / temporary block */
  44         sha256_hash_t hash;
  45
  46         r = (enc?0:(rounds-1));
  47         kbs = (keysize+7)/8;
  48         memcpy(tb+HALFSIZEB+2, key, kbs); /* copy key to temporary block */
  49         tb[HALFSIZEB+0] = 0;    /* set round counter high value to zero */
  50
  51         for(;r!=(enc?(rounds):-1);enc?r++:r--){ /* enc: 0..(rounds-1) ; !enc: (rounds-1)..0 */
  52                 memcpy(tb, R, HALFSIZEB); /* copy right half into tb */
  53                 tb[HALFSIZEB+1] = r;
  54                 sha256(&hash, tb, HALFSIZE+16+keysize);
  55                 if(!(r==(enc?(rounds-1):0))){
  56                         /* swap */
  57                         memxor(hash, L, HALFSIZE);
  58                         memcpy(L, R, HALFSIZE);
  59                         memcpy(R, hash, HALFSIZE);
  60                 } else {
  61                         /* no swap */
  62                         memxor(L, hash, HALFSIZE);
  63                 }
  64         }
  65 }
  66
  67