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1da177e4 LT |
1 | /* |
2 | * Cryptographic API | |
3 | * | |
4 | * ARC4 Cipher Algorithm | |
5 | * | |
6 | * Jon Oberheide <jon@oberheide.org> | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify | |
9 | * it under the terms of the GNU General Public License as published by | |
10 | * the Free Software Foundation; either version 2 of the License, or | |
11 | * (at your option) any later version. | |
12 | * | |
13 | */ | |
14 | #include <linux/module.h> | |
15 | #include <linux/init.h> | |
16 | #include <linux/crypto.h> | |
17 | ||
18 | #define ARC4_MIN_KEY_SIZE 1 | |
19 | #define ARC4_MAX_KEY_SIZE 256 | |
20 | #define ARC4_BLOCK_SIZE 1 | |
21 | ||
22 | struct arc4_ctx { | |
23 | u8 S[256]; | |
24 | u8 x, y; | |
25 | }; | |
26 | ||
6c2bb98b | 27 | static int arc4_set_key(struct crypto_tfm *tfm, const u8 *in_key, |
560c06ae | 28 | unsigned int key_len) |
1da177e4 | 29 | { |
6c2bb98b | 30 | struct arc4_ctx *ctx = crypto_tfm_ctx(tfm); |
1da177e4 LT |
31 | int i, j = 0, k = 0; |
32 | ||
33 | ctx->x = 1; | |
34 | ctx->y = 0; | |
35 | ||
36 | for(i = 0; i < 256; i++) | |
37 | ctx->S[i] = i; | |
38 | ||
39 | for(i = 0; i < 256; i++) | |
40 | { | |
41 | u8 a = ctx->S[i]; | |
42 | j = (j + in_key[k] + a) & 0xff; | |
43 | ctx->S[i] = ctx->S[j]; | |
44 | ctx->S[j] = a; | |
45 | if(++k >= key_len) | |
46 | k = 0; | |
47 | } | |
48 | ||
49 | return 0; | |
50 | } | |
51 | ||
6c2bb98b | 52 | static void arc4_crypt(struct crypto_tfm *tfm, u8 *out, const u8 *in) |
1da177e4 | 53 | { |
6c2bb98b | 54 | struct arc4_ctx *ctx = crypto_tfm_ctx(tfm); |
1da177e4 LT |
55 | |
56 | u8 *const S = ctx->S; | |
57 | u8 x = ctx->x; | |
58 | u8 y = ctx->y; | |
59 | u8 a, b; | |
60 | ||
61 | a = S[x]; | |
62 | y = (y + a) & 0xff; | |
63 | b = S[y]; | |
64 | S[x] = b; | |
65 | S[y] = a; | |
66 | x = (x + 1) & 0xff; | |
67 | *out++ = *in ^ S[(a + b) & 0xff]; | |
68 | ||
69 | ctx->x = x; | |
70 | ctx->y = y; | |
71 | } | |
72 | ||
73 | static struct crypto_alg arc4_alg = { | |
74 | .cra_name = "arc4", | |
75 | .cra_flags = CRYPTO_ALG_TYPE_CIPHER, | |
76 | .cra_blocksize = ARC4_BLOCK_SIZE, | |
77 | .cra_ctxsize = sizeof(struct arc4_ctx), | |
78 | .cra_module = THIS_MODULE, | |
79 | .cra_list = LIST_HEAD_INIT(arc4_alg.cra_list), | |
80 | .cra_u = { .cipher = { | |
81 | .cia_min_keysize = ARC4_MIN_KEY_SIZE, | |
82 | .cia_max_keysize = ARC4_MAX_KEY_SIZE, | |
83 | .cia_setkey = arc4_set_key, | |
84 | .cia_encrypt = arc4_crypt, | |
85 | .cia_decrypt = arc4_crypt } } | |
86 | }; | |
87 | ||
88 | static int __init arc4_init(void) | |
89 | { | |
90 | return crypto_register_alg(&arc4_alg); | |
91 | } | |
92 | ||
93 | ||
94 | static void __exit arc4_exit(void) | |
95 | { | |
96 | crypto_unregister_alg(&arc4_alg); | |
97 | } | |
98 | ||
99 | module_init(arc4_init); | |
100 | module_exit(arc4_exit); | |
101 | ||
102 | MODULE_LICENSE("GPL"); | |
103 | MODULE_DESCRIPTION("ARC4 Cipher Algorithm"); | |
104 | MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>"); |