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