chiark / gitweb /
Assume initial digits in a track name are a sort key even without the
[disorder] / lib / arcfour.c
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fcdff139
RK
1/* arcfour.c --- The arcfour stream cipher
2 * Copyright (C) 2000, 2001, 2002, 2003, 2005, 2006 Free Software
3 * Foundation, Inc.
4 *
5 * This file is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published
7 * by the Free Software Foundation; either version 2, or (at your
8 * option) any later version.
9 *
10 * This file is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this file; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 * 02110-1301, USA.
19 *
20 */
21
22/* Code from Libgcrypt adapted for gnulib by Simon Josefsson. */
23
24/*
25 * For a description of the algorithm, see:
26 * Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
27 * ISBN 0-471-11709-9. Pages 397 ff.
28 */
29
30#include "arcfour.h"
31
32void
33arcfour_stream (arcfour_context * context, const char *inbuf, char *outbuf,
34 size_t length)
35{
36 uint8_t i = context->idx_i;
37 uint8_t j = context->idx_j;
38 char *sbox = context->sbox;
39
40 for (; length > 0; length--)
41 {
42 char t;
43
44 i++;
45 j += sbox[i];
46 t = sbox[i];
47 sbox[i] = sbox[j];
48 sbox[j] = t;
49 *outbuf++ = (*inbuf++
50 ^ sbox[(0U + sbox[i] + sbox[j]) % ARCFOUR_SBOX_SIZE]);
51 }
52
53 context->idx_i = i;
54 context->idx_j = j;
55}
56
57void
58arcfour_setkey (arcfour_context * context, const char *key, size_t keylen)
59{
60 size_t i, j, k;
61 char *sbox = context->sbox;
62
63 context->idx_i = context->idx_j = 0;
64 for (i = 0; i < ARCFOUR_SBOX_SIZE; i++)
65 sbox[i] = i;
66 for (i = j = k = 0; i < ARCFOUR_SBOX_SIZE; i++)
67 {
68 char t;
69 j = (j + sbox[i] + key[k]) % ARCFOUR_SBOX_SIZE;
70 t = sbox[i];
71 sbox[i] = sbox[j];
72 sbox[j] = t;
73 if (++k == keylen)
74 k = 0;
75 }
76}