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         uint8_t ret = filter(s->odd);
  55
  56         feedin  = ret & !!is_encrypted;
  57         feedin ^= !!in;
  58         feedin ^= LF_POLY_ODD & s->odd;
  59         feedin ^= LF_POLY_EVEN & s->even;
  60         s->even = s->even << 1 | parity(feedin);
  61
  62         s->odd ^= (s->odd ^= s->even, s->even ^= s->odd);
  63
  64         return ret;
  65 }
  66 uint8_t crypto1_byte(struct Crypto1State *s, uint8_t in, int is_encrypted)
  67 {
  68         uint8_t i, ret = 0;
  69
  70         for (i = 0; i < 8; ++i)
  71                 ret |= crypto1_bit(s, BIT(in, i), is_encrypted) << i;
  72
  73         return ret;
  74 }
  75 uint32_t crypto1_word(struct Crypto1State *s, uint32_t in, int is_encrypted)
  76 {
  77         uint32_t i, ret = 0;
  78
  79         for (i = 0; i < 32; ++i)
  80                 ret |= crypto1_bit(s, BEBIT(in, i), is_encrypted) << (i ^ 24);
  81
  82         return ret;
  83 }
  84
  85 /* prng_successor
  86  * helper used to obscure the keystream during authentication
  87  */
  88 uint32_t prng_successor(uint32_t x, uint32_t n)
  89 {
  90         SWAPENDIAN(x);
  91         while(n--)
  92                 x = x >> 1 | (x >> 16 ^ x >> 18 ^ x >> 19 ^ x >> 21) << 31;
  93
  94         return SWAPENDIAN(x);
  95 }