1 /* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
2 /* ====================================================================
3 * Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in
14 * the documentation and/or other materials provided with the
17 * 3. All advertising materials mentioning features or use of this
18 * software must display the following acknowledgment:
19 * "This product includes software developed by the OpenSSL Project
20 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
23 * endorse or promote products derived from this software without
24 * prior written permission. For written permission, please contact
25 * openssl-core@openssl.org.
27 * 5. Products derived from this software may not be called "OpenSSL"
28 * nor may "OpenSSL" appear in their names without prior written
29 * permission of the OpenSSL Project.
31 * 6. Redistributions of any form whatsoever must retain the following
33 * "This product includes software developed by the OpenSSL Project
34 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
39 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
47 * OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
59 #include <openssl/aes.h>
62 /* NOTE: the IV/counter CTR mode is big-endian. The rest of the AES code
63 * is endian-neutral. */
65 /* increment counter (128-bit int) by 1 */
66 static void AES_ctr128_inc(unsigned char *counter) {
69 /* Grab bottom dword of counter and increment */
70 c = GETU32(counter + 12);
72 PUTU32(counter + 12, c);
74 /* if no overflow, we're done */
78 /* Grab 1st dword of counter and increment */
79 c = GETU32(counter + 8);
81 PUTU32(counter + 8, c);
83 /* if no overflow, we're done */
87 /* Grab 2nd dword of counter and increment */
88 c = GETU32(counter + 4);
90 PUTU32(counter + 4, c);
92 /* if no overflow, we're done */
96 /* Grab top dword of counter and increment */
97 c = GETU32(counter + 0);
99 PUTU32(counter + 0, c);
102 /* The input encrypted as though 128bit counter mode is being
103 * used. The extra state information to record how much of the
104 * 128bit block we have used is contained in *num, and the
105 * encrypted counter is kept in ecount_buf. Both *num and
106 * ecount_buf must be initialised with zeros before the first
107 * call to AES_ctr128_encrypt().
109 * This algorithm assumes that the counter is in the x lower bits
110 * of the IV (ivec), and that the application has full control over
111 * overflow and the rest of the IV. This implementation takes NO
112 * responsability for checking that the counter doesn't overflow
113 * into the rest of the IV when incremented.
115 EXPORT_C void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
116 const unsigned long length, const AES_KEY *key,
117 unsigned char ivec[AES_BLOCK_SIZE],
118 unsigned char ecount_buf[AES_BLOCK_SIZE],
122 unsigned long l=length;
124 assert(in && out && key && counter && num);
125 assert(*num < AES_BLOCK_SIZE);
131 AES_encrypt(ivec, ecount_buf, key);
132 AES_ctr128_inc(ivec);
134 *(out++) = *(in++) ^ ecount_buf[n];
135 n = (n+1) % AES_BLOCK_SIZE;