1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-or-later
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Cryptographic API
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * ARC4 Cipher Algorithm
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * Jon Oberheide <jon@oberheide.org>
8*4882a593Smuzhiyun */
9*4882a593Smuzhiyun
10*4882a593Smuzhiyun #include <crypto/arc4.h>
11*4882a593Smuzhiyun #include <linux/module.h>
12*4882a593Smuzhiyun
arc4_setkey(struct arc4_ctx * ctx,const u8 * in_key,unsigned int key_len)13*4882a593Smuzhiyun int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len)
14*4882a593Smuzhiyun {
15*4882a593Smuzhiyun int i, j = 0, k = 0;
16*4882a593Smuzhiyun
17*4882a593Smuzhiyun ctx->x = 1;
18*4882a593Smuzhiyun ctx->y = 0;
19*4882a593Smuzhiyun
20*4882a593Smuzhiyun for (i = 0; i < 256; i++)
21*4882a593Smuzhiyun ctx->S[i] = i;
22*4882a593Smuzhiyun
23*4882a593Smuzhiyun for (i = 0; i < 256; i++) {
24*4882a593Smuzhiyun u32 a = ctx->S[i];
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun j = (j + in_key[k] + a) & 0xff;
27*4882a593Smuzhiyun ctx->S[i] = ctx->S[j];
28*4882a593Smuzhiyun ctx->S[j] = a;
29*4882a593Smuzhiyun if (++k >= key_len)
30*4882a593Smuzhiyun k = 0;
31*4882a593Smuzhiyun }
32*4882a593Smuzhiyun
33*4882a593Smuzhiyun return 0;
34*4882a593Smuzhiyun }
35*4882a593Smuzhiyun EXPORT_SYMBOL(arc4_setkey);
36*4882a593Smuzhiyun
arc4_crypt(struct arc4_ctx * ctx,u8 * out,const u8 * in,unsigned int len)37*4882a593Smuzhiyun void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len)
38*4882a593Smuzhiyun {
39*4882a593Smuzhiyun u32 *const S = ctx->S;
40*4882a593Smuzhiyun u32 x, y, a, b;
41*4882a593Smuzhiyun u32 ty, ta, tb;
42*4882a593Smuzhiyun
43*4882a593Smuzhiyun if (len == 0)
44*4882a593Smuzhiyun return;
45*4882a593Smuzhiyun
46*4882a593Smuzhiyun x = ctx->x;
47*4882a593Smuzhiyun y = ctx->y;
48*4882a593Smuzhiyun
49*4882a593Smuzhiyun a = S[x];
50*4882a593Smuzhiyun y = (y + a) & 0xff;
51*4882a593Smuzhiyun b = S[y];
52*4882a593Smuzhiyun
53*4882a593Smuzhiyun do {
54*4882a593Smuzhiyun S[y] = a;
55*4882a593Smuzhiyun a = (a + b) & 0xff;
56*4882a593Smuzhiyun S[x] = b;
57*4882a593Smuzhiyun x = (x + 1) & 0xff;
58*4882a593Smuzhiyun ta = S[x];
59*4882a593Smuzhiyun ty = (y + ta) & 0xff;
60*4882a593Smuzhiyun tb = S[ty];
61*4882a593Smuzhiyun *out++ = *in++ ^ S[a];
62*4882a593Smuzhiyun if (--len == 0)
63*4882a593Smuzhiyun break;
64*4882a593Smuzhiyun y = ty;
65*4882a593Smuzhiyun a = ta;
66*4882a593Smuzhiyun b = tb;
67*4882a593Smuzhiyun } while (true);
68*4882a593Smuzhiyun
69*4882a593Smuzhiyun ctx->x = x;
70*4882a593Smuzhiyun ctx->y = y;
71*4882a593Smuzhiyun }
72*4882a593Smuzhiyun EXPORT_SYMBOL(arc4_crypt);
73*4882a593Smuzhiyun
74*4882a593Smuzhiyun MODULE_LICENSE("GPL");
75