components/wpa_supplicant/src/crypto/rc4.c (ESP-IDF)

/* * 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; }