crypto/rc4/rc4.cc

// Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <openssl/rc4.h>


void RC4(RC4_KEY *key, size_t len, const uint8_t *in, uint8_t *out) {
  uint32_t x = key->x;
  uint32_t y = key->y;
  uint32_t *d = key->data;

  for (size_t i = 0; i < len; i++) {
    x = (x + 1) & 0xff;
    uint32_t tx = d[x];
    y = (tx + y) & 0xff;
    uint32_t ty = d[y];
    d[x] = ty;
    d[y] = tx;
    out[i] = d[(tx + ty) & 0xff] ^ in[i];
  }

  key->x = x;
  key->y = y;
}

void RC4_set_key(RC4_KEY *rc4key, unsigned len, const uint8_t *key) {
  uint32_t *d = &rc4key->data[0];
  rc4key->x = 0;
  rc4key->y = 0;

  for (unsigned i = 0; i < 256; i++) {
    d[i] = i;
  }

  unsigned id1 = 0, id2 = 0;
  for (unsigned i = 0; i < 256; i++) {
    uint32_t tmp = d[i];
    id2 = (key[id1] + tmp + id2) & 0xff;
    if (++id1 == len) {
      id1 = 0;
    }
    d[i] = d[id2];
    d[id2] = tmp;
  }
}