1 /* ykcrc.c --- Implementation of YubiKey CRC-16 function.
2 *
3 * Written by Simon Josefsson <simon@josefsson.org>.
4 * Copyright (c) 2006-2012 Yubico AB
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are
9 * met:
10 *
11 * * Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 *
14 * * Redistributions in binary form must reproduce the above
15 * copyright notice, this list of conditions and the following
16 * disclaimer in the documentation and/or other materials provided
17 * with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 *
31 */
32
33 #include "yubikey.h"
34
35 uint16_t
yubikey_crc16(const uint8_t * buf,size_t buf_size)36 yubikey_crc16 (const uint8_t * buf, size_t buf_size)
37 {
38 uint16_t m_crc = 0xffff;
39
40 while (buf_size--)
41 {
42 int i, j;
43 m_crc ^= (uint8_t) * buf++ & 0xFF;
44 for (i = 0; i < 8; i++)
45 {
46 j = m_crc & 1;
47 m_crc >>= 1;
48 if (j)
49 m_crc ^= 0x8408;
50 }
51 }
52
53 return m_crc;
54 }
55