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>
63 * NOTE: the IV/counter CTR mode is big-endian. The rest of the AES code is
67 /* increment counter (128-bit int) by 1 */
68 static void AES_ctr128_inc(unsigned char *counter)
72 /* Grab bottom dword of counter and increment */
73 c = GETU32(counter + 12);
76 PUTU32(counter + 12, c);
78 /* if no overflow, we're done */
82 /* Grab 1st dword of counter and increment */
83 c = GETU32(counter + 8);
86 PUTU32(counter + 8, c);
88 /* if no overflow, we're done */
92 /* Grab 2nd dword of counter and increment */
93 c = GETU32(counter + 4);
96 PUTU32(counter + 4, c);
98 /* if no overflow, we're done */
102 /* Grab top dword of counter and increment */
103 c = GETU32(counter + 0);
106 PUTU32(counter + 0, c);
110 * The input encrypted as though 128bit counter mode is being used. The
111 * extra state information to record how much of the 128bit block we have
112 * used is contained in *num, and the encrypted counter is kept in
113 * ecount_buf. Both *num and ecount_buf must be initialised with zeros
114 * before the first call to AES_ctr128_encrypt(). This algorithm assumes
115 * that the counter is in the x lower bits of the IV (ivec), and that the
116 * application has full control over overflow and the rest of the IV. This
117 * implementation takes NO responsability for checking that the counter
118 * doesn't overflow into the rest of the IV when incremented.
120 void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
121 const unsigned long length, const AES_KEY *key,
122 unsigned char ivec[AES_BLOCK_SIZE],
123 unsigned char ecount_buf[AES_BLOCK_SIZE],
128 unsigned long l = length;
130 assert(in && out && key && counter && num);
131 assert(*num < AES_BLOCK_SIZE);
137 AES_encrypt(ivec, ecount_buf, key);
138 AES_ctr128_inc(ivec);
140 *(out++) = *(in++) ^ ecount_buf[n];
141 n = (n + 1) % AES_BLOCK_SIZE;