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| /*
| * RC4 stream cipher
| * Copyright (c) 2002-2005, Jouni Malinen <j@w1.fi>
| *
| * This software may be distributed under the terms of the BSD license.
| * See README for more details.
| */
|
| #include "includes.h"
|
| #include "common.h"
| #include "crypto.h"
|
| #define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0)
|
| int rc4_skip(const u8 *key, size_t keylen, size_t skip,
| u8 *data, size_t data_len)
| {
| u32 i, j, k;
| u8 S[256], *pos;
| size_t kpos;
|
| /* Setup RC4 state */
| for (i = 0; i < 256; i++)
| S[i] = i;
| j = 0;
| kpos = 0;
| for (i = 0; i < 256; i++) {
| j = (j + S[i] + key[kpos]) & 0xff;
| kpos++;
| if (kpos >= keylen)
| kpos = 0;
| S_SWAP(i, j);
| }
|
| /* Skip the start of the stream */
| i = j = 0;
| for (k = 0; k < skip; k++) {
| i = (i + 1) & 0xff;
| j = (j + S[i]) & 0xff;
| S_SWAP(i, j);
| }
|
| /* Apply RC4 to data */
| pos = data;
| for (k = 0; k < data_len; k++) {
| i = (i + 1) & 0xff;
| j = (j + S[i]) & 0xff;
| S_SWAP(i, j);
| *pos++ ^= S[(S[i] + S[j]) & 0xff];
| }
|
| return 0;
| }
|
|
