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/* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
/* ====================================================================
* Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@openssl.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
*/
#ifndef AES_DEBUG
# ifndef NDEBUG
# define NDEBUG
# endif
#endif
#include <assert.h>
#include <openssl/aes.h>
#include "aes_locl.h"
/* NOTE: CTR mode is big-endian. The rest of the AES code
* is endian-neutral. */
/* increment counter (128-bit int) by 1 */
static void AES_ctr128_inc(unsigned char *counter) {
unsigned long c;
/* Grab bottom dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 0);
c++;
PUTU32(counter + 0, c);
#else
c = GETU32(counter + 12);
c++;
PUTU32(counter + 12, c);
#endif
/* if no overflow, we're done */
if (c)
return;
/* Grab 1st dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 4);
c++;
PUTU32(counter + 4, c);
#else
c = GETU32(counter + 8);
c++;
PUTU32(counter + 8, c);
#endif
/* if no overflow, we're done */
if (c)
return;
/* Grab 2nd dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 8);
c++;
PUTU32(counter + 8, c);
#else
c = GETU32(counter + 4);
c++;
PUTU32(counter + 4, c);
#endif
/* if no overflow, we're done */
if (c)
return;
/* Grab top dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 12);
c++;
PUTU32(counter + 12, c);
#else
c = GETU32(counter + 0);
c++;
PUTU32(counter + 0, c);
#endif
}
/* The input encrypted as though 128bit counter mode is being
* used. The extra state information to record how much of the
* 128bit block we have used is contained in *num, and the
* encrypted counter is kept in ecount_buf. Both *num and
* ecount_buf must be initialised with zeros before the first
* call to AES_ctr128_encrypt().
*
* This algorithm assumes that the counter is in the x lower bits
* of the IV (ivec), and that the application has full control over
* overflow and the rest of the IV. This implementation takes NO
* responsability for checking that the counter doesn't overflow
* into the rest of the IV when incremented.
*/
void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
const unsigned long length, const AES_KEY *key,
unsigned char ivec[AES_BLOCK_SIZE],
unsigned char ecount_buf[AES_BLOCK_SIZE],
unsigned int *num) {
unsigned int n;
unsigned long l=length;
assert(in && out && key && counter && num);
assert(*num < AES_BLOCK_SIZE);
n = *num;
while (l--) {
if (n == 0) {
AES_encrypt(ivec, ecount_buf, key);
AES_ctr128_inc(ivec);
}
*(out++) = *(in++) ^ ecount_buf[n];
n = (n+1) % AES_BLOCK_SIZE;
}
*num=n;
}
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