1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * Cryptographic API |
4 | * |
5 | * ARC4 Cipher Algorithm |
6 | * |
7 | * Jon Oberheide <jon@oberheide.org> |
8 | */ |
9 | |
10 | #include <crypto/arc4.h> |
11 | #include <linux/module.h> |
12 | |
13 | int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len) |
14 | { |
15 | int i, j = 0, k = 0; |
16 | |
17 | ctx->x = 1; |
18 | ctx->y = 0; |
19 | |
20 | for (i = 0; i < 256; i++) |
21 | ctx->S[i] = i; |
22 | |
23 | for (i = 0; i < 256; i++) { |
24 | u32 a = ctx->S[i]; |
25 | |
26 | j = (j + in_key[k] + a) & 0xff; |
27 | ctx->S[i] = ctx->S[j]; |
28 | ctx->S[j] = a; |
29 | if (++k >= key_len) |
30 | k = 0; |
31 | } |
32 | |
33 | return 0; |
34 | } |
35 | EXPORT_SYMBOL(arc4_setkey); |
36 | |
37 | void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len) |
38 | { |
39 | u32 *const S = ctx->S; |
40 | u32 x, y, a, b; |
41 | u32 ty, ta, tb; |
42 | |
43 | if (len == 0) |
44 | return; |
45 | |
46 | x = ctx->x; |
47 | y = ctx->y; |
48 | |
49 | a = S[x]; |
50 | y = (y + a) & 0xff; |
51 | b = S[y]; |
52 | |
53 | do { |
54 | S[y] = a; |
55 | a = (a + b) & 0xff; |
56 | S[x] = b; |
57 | x = (x + 1) & 0xff; |
58 | ta = S[x]; |
59 | ty = (y + ta) & 0xff; |
60 | tb = S[ty]; |
61 | *out++ = *in++ ^ S[a]; |
62 | if (--len == 0) |
63 | break; |
64 | y = ty; |
65 | a = ta; |
66 | b = tb; |
67 | } while (true); |
68 | |
69 | ctx->x = x; |
70 | ctx->y = y; |
71 | } |
72 | EXPORT_SYMBOL(arc4_crypt); |
73 | |
74 | MODULE_LICENSE("GPL" ); |
75 | |