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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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