aes-ctr.c

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/*
 * AES-128 CTR
 *
 * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "aes.h"
#include "aes_wrap.h"

int aes_128_ctr_encrypt(const u8 *key, const u8 *nonce,
                        u8 *data, size_t data_len)
{
        void *ctx;
        size_t j, len, left = data_len;
        int i;
        u8 *pos = data;
        u8 counter[AES_BLOCK_SIZE], buf[AES_BLOCK_SIZE];

        ctx = aes_encrypt_init(key, 16);
        if (ctx == NULL)
                return -1;
        os_memcpy(counter, nonce, AES_BLOCK_SIZE);

        while (left > 0) {
                aes_encrypt(ctx, counter, buf);

                len = (left < AES_BLOCK_SIZE) ? left : AES_BLOCK_SIZE;
                for (j = 0; j < len; j++)
                        pos[j] ^= buf[j];
                pos += len;
                left -= len;

                for (i = AES_BLOCK_SIZE - 1; i >= 0; i--) {
                        counter[i]++;
                        if (counter[i])
                                break;
                }
        }
        aes_encrypt_deinit(ctx);
        return 0;
}