1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * (C) Copyright 2015 Google, Inc
4 *
5 * (C) Copyright 2008-2014 Rockchip Electronics
6 *
7 * Rivest Cipher 4 (RC4) implementation
8 */
9
10#include <rc4.h>
11
12void rc4_encode(unsigned char *buf, unsigned int len, const unsigned char key[16])
13{
14	unsigned char s[256], k[256], temp;
15	unsigned short i, j, t;
16	int ptr;
17
18	j = 0;
19	for (i = 0; i < 256; i++) {
20		s[i] = (unsigned char)i;
21		j &= 0x0f;
22		k[i] = key[j];
23		j++;
24	}
25
26	j = 0;
27	for (i = 0; i < 256; i++) {
28		j = (j + s[i] + k[i]) % 256;
29		temp = s[i];
30		s[i] = s[j];
31		s[j] = temp;
32	}
33
34	i = 0;
35	j = 0;
36	for (ptr = 0; ptr < len; ptr++) {
37		i = (i + 1) % 256;
38		j = (j + s[i]) % 256;
39		temp = s[i];
40		s[i] = s[j];
41		s[j] = temp;
42		t = (s[i] + (s[j] % 256)) % 256;
43		buf[ptr] = buf[ptr] ^ s[t];
44	}
45}
46