18d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt/* 28d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt * RC4 stream cipher 38d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt * Copyright (c) 2002-2005, Jouni Malinen <j@w1.fi> 48d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt * 5c5ec7f57ead87efa365800228aa0b09a12d9e6c4Dmitry Shmidt * This software may be distributed under the terms of the BSD license. 6c5ec7f57ead87efa365800228aa0b09a12d9e6c4Dmitry Shmidt * See README for more details. 78d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt */ 88d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 98d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt#include "includes.h" 108d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 118d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt#include "common.h" 128d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt#include "crypto.h" 138d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 148d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt#define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0) 158d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 168d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidtint rc4_skip(const u8 *key, size_t keylen, size_t skip, 178d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt u8 *data, size_t data_len) 188d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt{ 198d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt u32 i, j, k; 208d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt u8 S[256], *pos; 218d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt size_t kpos; 228d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 238d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt /* Setup RC4 state */ 248d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt for (i = 0; i < 256; i++) 258d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt S[i] = i; 268d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt j = 0; 278d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt kpos = 0; 288d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt for (i = 0; i < 256; i++) { 298d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt j = (j + S[i] + key[kpos]) & 0xff; 308d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt kpos++; 318d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt if (kpos >= keylen) 328d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt kpos = 0; 338d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt S_SWAP(i, j); 348d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt } 358d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 368d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt /* Skip the start of the stream */ 378d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt i = j = 0; 388d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt for (k = 0; k < skip; k++) { 398d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt i = (i + 1) & 0xff; 408d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt j = (j + S[i]) & 0xff; 418d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt S_SWAP(i, j); 428d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt } 438d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 448d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt /* Apply RC4 to data */ 458d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt pos = data; 468d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt for (k = 0; k < data_len; k++) { 478d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt i = (i + 1) & 0xff; 488d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt j = (j + S[i]) & 0xff; 498d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt S_SWAP(i, j); 508d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt *pos++ ^= S[(S[i] + S[j]) & 0xff]; 518d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt } 528d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt 538d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt return 0; 548d520ff1dc2da35cdca849e982051b86468016d8Dmitry Shmidt} 55