shabea/shabea.c

   1 /* shabea.c */
   2 /*
   3  *   This file is part of AnonAccess, an access system which can be used
   4  *    to open door or doing other things with an anonymity featured
   5  *    account managment.
   6  *   Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)
   7  *
   8  *   This program is free software: you can redistribute it and/or modify
   9  *   it under the terms of the GNU General Public License as published by
  10  *   the Free Software Foundation, either version 3 of the License, or
  11  *   (at your option) any later version.
  12  *
  13  *   This program is distributed in the hope that it will be useful,
  14  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *   GNU General Public License for more details.
  17  *
  18  *   You should have received a copy of the GNU General Public License
  19  *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20  */
  21
  22 /**
  23  * \file        shabea.c
  24  * \author      Daniel Otte
  25  * \date        2007-06-07
  26  * \brief       SHABEA - a SHA Based Encryption Algorithm implementation
  27  * \par License
  28  * GPL
  29  *
  30  * SHABEAn-r where n is the blocksize and r the number of round used
  31  *
  32  *
  33  */
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include "sha256.h"
  37
  38 #include "config.h"
  39 #include "memxor.h"
  40
  41
  42 /*
  43  * SHABEA256-n
  44  */
  45
  46 #define SHABEA_BLOCKSIZE 256
  47 #define SHABEA_BLOCKSIZEB (SHABEA_BLOCKSIZE/8)
  48 #define SHABEA_HALFSIZEB  (SHABEA_BLOCKSIZEB/2)
  49 #define SHABEA_HALFSIZE (SHABEA_BLOCKSIZE/2)
  50
  51 #define L ((uint8_t*)block+ 0)
  52 #define R ((uint8_t*)block+16)
  53 void shabea256(void * block, void * key, uint16_t keysize_b, uint8_t enc, uint8_t rounds){
  54         uint8_t r;              /**/
  55         uint8_t tb[SHABEA_HALFSIZEB+2+(keysize_b+7)/8]; /**/
  56         uint16_t kbs;   /* bytes used for the key / temporary block */
  57         sha256_hash_t hash;
  58         uint8_t termcond;
  59         int8_t dir;
  60         if(enc){
  61                 r = 0;
  62                 termcond = rounds-1;
  63                 dir = 1;
  64         } else {
  65                 r = rounds-1;
  66                 termcond = 0;
  67                 dir = -1;
  68         }
  69         kbs = (keysize_b+7)/8;
  70         memcpy(tb+SHABEA_HALFSIZEB+2, key, kbs); /* copy key to temporary block */
  71         tb[SHABEA_HALFSIZEB+0] = 0;     /* set round counter high value to zero */
  72
  73         for(;;r+=dir){ /* enc: 0..(rounds-1) ; !enc: (rounds-1)..0 */
  74                 memcpy(tb, R, SHABEA_HALFSIZEB); /* copy right half into tb */
  75                 tb[SHABEA_HALFSIZEB+1] = r;
  76                 sha256(&hash, tb, SHABEA_HALFSIZE+16+keysize_b);
  77                 if(r!=termcond){
  78                         /* swap */
  79                         memxor(hash, L, SHABEA_HALFSIZEB);
  80                         memcpy(L, R, SHABEA_HALFSIZEB);
  81                         memcpy(R, hash, SHABEA_HALFSIZEB);
  82                 } else {
  83                         /* last round */
  84                         /* no swap */
  85                         memxor(L, hash, SHABEA_HALFSIZEB);
  86                         return;
  87                 }
  88         }
  89 }
  90
  91