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109 lines
2.8 KiB
C
109 lines
2.8 KiB
C
/*
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* dlls/rsaenh/rc4.c
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* RC4 functions
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*
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* Copyright 2004 Michael Jung
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* Based on public domain code by Tom St Denis (tomstdenis@iahu.ca)
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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/*
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* This file contains code from the LibTomCrypt cryptographic
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* library written by Tom St Denis (tomstdenis@iahu.ca). LibTomCrypt
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* is in the public domain. The code in this file is tailored to
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* special requirements. Take a look at http://libtomcrypt.org for the
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* original version.
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*/
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#include "tomcrypt.h"
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int rc4_start(prng_state *prng)
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{
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/* set keysize to zero */
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prng->rc4.x = 0;
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return CRYPT_OK;
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}
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int rc4_add_entropy(const unsigned char *buf, unsigned long len, prng_state *prng)
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{
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/* trim as required */
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if (prng->rc4.x + len > 256) {
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if (prng->rc4.x == 256) {
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/* I can't possibly accept another byte, ok maybe a mint wafer... */
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return CRYPT_OK;
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} else {
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/* only accept part of it */
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len = 256 - prng->rc4.x;
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}
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}
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while (len--) {
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prng->rc4.buf[prng->rc4.x++] = *buf++;
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}
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return CRYPT_OK;
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}
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int rc4_ready(prng_state *prng)
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{
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unsigned char key[256], tmp, *s;
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int keylen, x, y, j;
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/* extract the key */
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s = prng->rc4.buf;
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memcpy(key, s, 256);
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keylen = prng->rc4.x;
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/* make RC4 perm and shuffle */
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for (x = 0; x < 256; x++) {
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s[x] = x;
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}
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for (j = x = y = 0; x < 256; x++) {
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y = (y + prng->rc4.buf[x] + key[j++]) & 255;
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if (j == keylen) {
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j = 0;
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}
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tmp = s[x]; s[x] = s[y]; s[y] = tmp;
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}
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prng->rc4.x = 0;
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prng->rc4.y = 0;
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return CRYPT_OK;
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}
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unsigned long rc4_read(unsigned char *buf, unsigned long len, prng_state *prng)
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{
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unsigned char x, y, *s, tmp;
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unsigned long n;
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n = len;
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x = prng->rc4.x;
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y = prng->rc4.y;
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s = prng->rc4.buf;
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while (len--) {
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x = (x + 1) & 255;
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y = (y + s[x]) & 255;
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tmp = s[x]; s[x] = s[y]; s[y] = tmp;
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tmp = (s[x] + s[y]) & 255;
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*buf++ ^= s[tmp];
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}
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prng->rc4.x = x;
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prng->rc4.y = y;
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return n;
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}
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