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 
rc4_encode(unsigned char * buf,unsigned int len,const unsigned char key[16])12 void 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