armsrc/crypto1.c

   1 /*  crypto1.c
   2
   3         This program is free software; you can redistribute it and/or
   4         modify it under the terms of the GNU General Public License
   5         as published by the Free Software Foundation; either version 2
   6         of the License, or (at your option) any later version.
   7
   8         This program is distributed in the hope that it will be useful,
   9         but WITHOUT ANY WARRANTY; without even the implied warranty of
  10         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11         GNU General Public License for more details.
  12
  13         You should have received a copy of the GNU General Public License
  14         along with this program; if not, write to the Free Software
  15         Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  16         MA  02110-1301, US
  17
  18         Copyright (C) 2008-2008 bla <blapost@gmail.com>
  19 */
  20 #include "crapto1.h"
  21 #include <stdlib.h>
  22
  23 #define SWAPENDIAN(x)\
  24         (x = (x >> 8 & 0xff00ff) | (x & 0xff00ff) << 8, x = x >> 16 | x << 16)
  25
  26 void crypto1_create(struct Crypto1State *s, uint64_t key)
  27 {
  28 //      struct Crypto1State *s = malloc(sizeof(*s));
  29         int i;
  30
  31         for(i = 47;s && i > 0; i -= 2) {
  32                 s->odd  = s->odd  << 1 | BIT(key, (i - 1) ^ 7);
  33                 s->even = s->even << 1 | BIT(key, i ^ 7);
  34         }
  35         return;
  36 }
  37 void crypto1_destroy(struct Crypto1State *state)
  38 {
  39 //      free(state);
  40         state->odd = 0;
  41         state->even = 0;
  42 }
  43 void crypto1_get_lfsr(struct Crypto1State *state, uint64_t *lfsr)
  44 {
  45         int i;
  46         for(*lfsr = 0, i = 23; i >= 0; --i) {
  47                 *lfsr = *lfsr << 1 | BIT(state->odd, i ^ 3);
  48                 *lfsr = *lfsr << 1 | BIT(state->even, i ^ 3);
  49         }
  50 }
  51 uint8_t crypto1_bit(struct Crypto1State *s, uint8_t in, int is_encrypted)
  52 {
  53         uint32_t feedin;
  54         uint32_t tmp;
  55         uint8_t ret = filter(s->odd);
  56
  57         feedin  = ret & !!is_encrypted;
  58         feedin ^= !!in;
  59         feedin ^= LF_POLY_ODD & s->odd;
  60         feedin ^= LF_POLY_EVEN & s->even;
  61         s->even = s->even << 1 | parity(feedin);
  62
  63         tmp = s->odd;
  64         s->odd = s->even;
  65         s->even = tmp;
  66
  67         return ret;
  68 }
  69 uint8_t crypto1_byte(struct Crypto1State *s, uint8_t in, int is_encrypted)
  70 {
  71         uint8_t i, ret = 0;
  72
  73         for (i = 0; i < 8; ++i)
  74                 ret |= crypto1_bit(s, BIT(in, i), is_encrypted) << i;
  75
  76         return ret;
  77 }
  78 uint32_t crypto1_word(struct Crypto1State *s, uint32_t in, int is_encrypted)
  79 {
  80         uint32_t i, ret = 0;
  81
  82         for (i = 0; i < 32; ++i)
  83                 ret |= crypto1_bit(s, BEBIT(in, i), is_encrypted) << (i ^ 24);
  84
  85         return ret;
  86 }
  87
  88 /* prng_successor
  89  * helper used to obscure the keystream during authentication
  90  */
  91 uint32_t prng_successor(uint32_t x, uint32_t n)
  92 {
  93         SWAPENDIAN(x);
  94         while(n--)
  95                 x = x >> 1 | (x >> 16 ^ x >> 18 ^ x >> 19 ^ x >> 21) << 31;
  96
  97         return SWAPENDIAN(x);
  98 }