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/*
* Copyright (c) 2007, Cameron Rich
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* * Neither the name of the axTLS project nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* An implementation of the RC4/ARC4 algorithm.
* Originally written by Christophe Devine.
*/
#include <string.h>
#include "crypto.h"
/**
* Get ready for an encrypt/decrypt operation
*/
void RC4_setup(RC4_CTX *ctx, const uint8_t *key, int length)
{
int i, j = 0, k = 0, a;
uint8_t *m;
ctx->x = 0;
ctx->y = 0;
m = ctx->m;
for (i = 0; i < 256; i++)
m[i] = i;
for (i = 0; i < 256; i++)
{
a = m[i];
j = (uint8_t)(j + a + key[k]);
m[i] = m[j];
m[j] = a;
if (++k >= length)
k = 0;
}
}
/**
* Perform the encrypt/decrypt operation (can use it for either since
* this is a stream cipher).
*/
void RC4_crypt(RC4_CTX *ctx, const uint8_t *msg, uint8_t *out, int length)
{
int i;
uint8_t *m, x, y, a, b;
out = (uint8_t *)msg;
x = ctx->x;
y = ctx->y;
m = ctx->m;
for (i = 0; i < length; i++)
{
a = m[++x];
y += a;
m[x] = b = m[y];
m[y] = a;
out[i] ^= m[(uint8_t)(a + b)];
}
ctx->x = x;
ctx->y = y;
}
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