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