3 * The arcfour/rc4 stream cipher.
6 /* nettle, low-level cryptographics library
8 * Copyright (C) 2001 Niels Möller
10 * The nettle library is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU Lesser General Public License as published by
12 * the Free Software Foundation; either version 2.1 of the License, or (at your
13 * option) any later version.
15 * The nettle library is distributed in the hope that it will be useful, but
16 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
17 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
18 * License for more details.
20 * You should have received a copy of the GNU Lesser General Public License
21 * along with the nettle library; see the file COPYING.LIB. If not, write to
22 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
34 #define SWAP(a,b) do { int _t = a; a = b; b = _t; } while(0)
37 arcfour_set_key(struct arcfour_ctx *ctx,
38 unsigned length, const uint8_t *key)
42 assert(length >= ARCFOUR_MIN_KEY_SIZE);
43 assert(length <= ARCFOUR_MAX_KEY_SIZE);
45 /* Initialize context */
46 for (i = 0; i<256; i++)
49 for (i = j = k = 0; i<256; i++)
51 j += ctx->S[i] + key[k]; j &= 0xff;
52 SWAP(ctx->S[i], ctx->S[j]);
53 /* Repeat key as needed */