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