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/*
* RC4 functions for HTMLDOC.
*
* Original code by Tim Martin
* Copyright 1999 by Carnegie Mellon University, All Rights Reserved
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose and without fee is hereby granted,
* provided that the above copyright notice appear in all copies and that
* both that copyright notice and this permission notice appear in
* supporting documentation, and that the name of Carnegie Mellon
* University not be used in advertising or publicity pertaining to
* distribution of the software without specific, written prior
* permission.
*
* CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE FOR
* ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Contents:
*
* rc4_init() - Initialize an RC4 context with the specified key.
* rc4_encrypt() - Encrypt the given buffer.
*/
#include "rc4.h"
/*
* 'rc4_init()' - Initialize an RC4 context with the specified key.
*/
void
rc4_init(rc4_context_t *text, /* IO - Context */
const unsigned char *key, /* I - Key */
unsigned keylen) /* I - Length of key */
{
int i, j; /* Looping vars */
unsigned char tmp; /* Temporary variable */
/*
* Fill in linearly s0=0, s1=1, ...
*/
for (i = 0; i < 256; i ++)
text->sbox[i] = i;
for (i = 0, j = 0; i < 256; i ++)
{
/*
* j = (j + Si + Ki) mod 256
*/
j = (j + text->sbox[i] + key[i % keylen]) & 255;
/*
* Swap Si and Sj...
*/
tmp = text->sbox[i];
text->sbox[i] = text->sbox[j];
text->sbox[j] = tmp;
}
/*
* Initialized counters to 0 and return...
*/
text->i = 0;
text->j = 0;
}
/*
* 'rc4_encrypt()' - Encrypt the given buffer.
*/
void
rc4_encrypt(rc4_context_t *text, /* I - Context */
const unsigned char *input, /* I - Input buffer */
unsigned char *output, /* O - Output buffer */
unsigned len) /* I - Size of buffers */
{
unsigned char tmp; /* Swap variable */
int i, j; /* Looping vars */
int t; /* Current S box */
/*
* Loop through the entire buffer...
*/
i = text->i;
j = text->j;
while (len > 0)
{
/*
* Get the next S box indices...
*/
i = (i + 1) & 255;
j = (j + text->sbox[i]) & 255;
/*
* Swap Si and Sj...
*/
tmp = text->sbox[i];
text->sbox[i] = text->sbox[j];
text->sbox[j] = tmp;
/*
* Get the S box index for this byte...
*/
t = (text->sbox[i] + text->sbox[j]) & 255;
/*
* Encrypt using the S box...
*/
*output++ = *input++ ^ text->sbox[t];
len --;
}
/*
* Copy current S box indices back to context...
*/
text->i = i;
text->j = j;
}
/*
* End of "$Id$".
*/
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