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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 | |
27 | static int arc4_set_key(struct crypto_tfm *tfm, const u8 *in_key, |
28 | unsigned int key_len) |
29 | { |
30 | struct arc4_ctx *ctx = crypto_tfm_ctx(tfm); |
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 | |
52 | static void arc4_crypt(struct crypto_tfm *tfm, u8 *out, const u8 *in) |
53 | { |
54 | struct arc4_ctx *ctx = crypto_tfm_ctx(tfm); |
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>"); |
105 |
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