1 /*
2 * dlls/rsaenh/rc4.c
3 * RC4 functions
4 *
5 * Copyright 2004 Michael Jung
6 * Based on public domain code by Tom St Denis (tomstdenis@iahu.ca)
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library 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 GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
21 */
22
23 /*
24 * This file contains code from the LibTomCrypt cryptographic
25 * library written by Tom St Denis (tomstdenis@iahu.ca). LibTomCrypt
26 * is in the public domain. The code in this file is tailored to
27 * special requirements. Take a look at http://libtomcrypt.org for the
28 * original version.
29 */
30
31 #include "tomcrypt.h"
32
33 int rc4_start(prng_state *prng)
34 {
35 /* set keysize to zero */
36 prng->rc4.x = 0;
37
38 return CRYPT_OK;
39 }
40
41 int rc4_add_entropy(const unsigned char *buf, unsigned long len, prng_state *prng)
42 {
43 /* trim as required */
44 if (prng->rc4.x + len > 256) {
45 if (prng->rc4.x == 256) {
46 /* I can't possibly accept another byte, ok maybe a mint wafer... */
47 return CRYPT_OK;
48 } else {
49 /* only accept part of it */
50 len = 256 - prng->rc4.x;
51 }
52 }
53
54 while (len--) {
55 prng->rc4.buf[prng->rc4.x++] = *buf++;
56 }
57
58 return CRYPT_OK;
59 }
60
61 int rc4_ready(prng_state *prng)
62 {
63 unsigned char key[256], tmp, *s;
64 int keylen, x, y, j;
65
66 /* extract the key */
67 s = prng->rc4.buf;
68 memcpy(key, s, 256);
69 keylen = prng->rc4.x;
70
71 /* make RC4 perm and shuffle */
72 for (x = 0; x < 256; x++) {
73 s[x] = x;
74 }
75
76 for (j = x = y = 0; x < 256; x++) {
77 y = (y + prng->rc4.buf[x] + key[j++]) & 255;
78 if (j == keylen) {
79 j = 0;
80 }
81 tmp = s[x]; s[x] = s[y]; s[y] = tmp;
82 }
83 prng->rc4.x = 0;
84 prng->rc4.y = 0;
85
86 return CRYPT_OK;
87 }
88
89 unsigned long rc4_read(unsigned char *buf, unsigned long len, prng_state *prng)
90 {
91 unsigned char x, y, *s, tmp;
92 unsigned long n;
93
94 n = len;
95 x = prng->rc4.x;
96 y = prng->rc4.y;
97 s = prng->rc4.buf;
98 while (len--) {
99 x = (x + 1) & 255;
100 y = (y + s[x]) & 255;
101 tmp = s[x]; s[x] = s[y]; s[y] = tmp;
102 tmp = (s[x] + s[y]) & 255;
103 *buf++ ^= s[tmp];
104 }
105 prng->rc4.x = x;
106 prng->rc4.y = y;
107 return n;
108 }
109
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