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/*! \file rc4.c
\brief Source file for RC4 stream cipher routines
\author Damien Miller <djm@mindrot.org>
\version 0.0.0
\date 1999
A simple implementation of the RC4 stream cipher, based on the
description given in _Bruce Schneier's_ "Applied Cryptography"
2nd edition.
Copyright 1999 Damien Miller
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy,
modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
AND NONINFRINGEMENT. IN NO EVENT SHALL DAMIEN MILLER BE LIABLE
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
\warning None of these functions clears its memory after use. It
\warning is the responsability of the calling routines to ensure
\warning that any sensitive data (keystream, key or plaintext) is
\warning properly erased after use.
\warning The name "RC4" is trademarked in the United States,
\warning you may need to use "RC4 compatible" or "ARC4"
\warning (Alleged RC4).
*/
/* $Id: rc4.c,v 1.1.1.1 1999/10/26 05:48:13 damien Exp $ */
#include "rc4.h"
void rc4_key(rc4_t *r, unsigned char *key, int len)
{
int t;
for(r->i = 0; r->i < 256; r->i++)
r->s[r->i] = r->i;
r->j = 0;
for(r->i = 0; r->i < 256; r->i++)
{
r->j = (r->j + r->s[r->i] + key[r->i % len]) % 256;
t = r->s[r->i];
r->s[r->i] = r->s[r->j];
r->s[r->j] = t;
}
r->i = r->j = 0;
}
void rc4_crypt(rc4_t *r, unsigned char *plaintext, int len)
{
int t;
int c;
c = 0;
while(c < len)
{
r->i = (r->i + 1) % 256;
r->j = (r->j + r->s[r->i]) % 256;
t = r->s[r->i];
r->s[r->i] = r->s[r->j];
r->s[r->j] = t;
t = (r->s[r->i] + r->s[r->j]) % 256;
plaintext[c] ^= r->s[t];
c++;
}
}
void rc4_getbytes(rc4_t *r, unsigned char *buffer, int len)
{
int t;
int c;
c = 0;
while(c < len)
{
r->i = (r->i + 1) % 256;
r->j = (r->j + r->s[r->i]) % 256;
t = r->s[r->i];
r->s[r->i] = r->s[r->j];
r->s[r->j] = t;
t = (r->s[r->i] + r->s[r->j]) % 256;
buffer[c] = r->s[t];
c++;
}
}
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