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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 struct Crypto1State * crypto1_create(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 s;
36 }
37 void crypto1_destroy(struct Crypto1State *state)
38 {
39 free(state);
40 }
41 void crypto1_get_lfsr(struct Crypto1State *state, uint64_t *lfsr)
42 {
43 int i;
44 for(*lfsr = 0, i = 23; i >= 0; --i) {
45 *lfsr = *lfsr << 1 | BIT(state->odd, i ^ 3);
46 *lfsr = *lfsr << 1 | BIT(state->even, i ^ 3);
47 }
48 }
49 uint8_t crypto1_bit(struct Crypto1State *s, uint8_t in, int is_encrypted)
50 {
51 uint32_t feedin;
52 uint8_t ret = filter(s->odd);
53
54 feedin = ret & !!is_encrypted;
55 feedin ^= !!in;
56 feedin ^= LF_POLY_ODD & s->odd;
57 feedin ^= LF_POLY_EVEN & s->even;
58 s->even = s->even << 1 | parity(feedin);
59
60 s->odd ^= (s->odd ^= s->even, s->even ^= s->odd);
61
62 return ret;
63 }
64 uint8_t crypto1_byte(struct Crypto1State *s, uint8_t in, int is_encrypted)
65 {
66 uint8_t i, ret = 0;
67
68 for (i = 0; i < 8; ++i)
69 ret |= crypto1_bit(s, BIT(in, i), is_encrypted) << i;
70
71 return ret;
72 }
73 uint32_t crypto1_word(struct Crypto1State *s, uint32_t in, int is_encrypted)
74 {
75 uint32_t i, ret = 0;
76
77 for (i = 0; i < 4; ++i, in <<= 8)
78 ret = ret << 8 | crypto1_byte(s, in >> 24, is_encrypted);
79
80 return ret;
81 }
82
83 /* prng_successor
84 * helper used to obscure the keystream during authentication
85 */
86 uint32_t prng_successor(uint32_t x, uint32_t n)
87 {
88 SWAPENDIAN(x);
89 while(n--)
90 x = x >> 1 | (x >> 16 ^ x >> 18 ^ x >> 19 ^ x >> 21) << 31;
91
92 return SWAPENDIAN(x);
93 }
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