/* * 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; }

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