mirror of
https://github.com/RfidResearchGroup/proxmark3.git
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101 lines
2.9 KiB
C
101 lines
2.9 KiB
C
//-----------------------------------------------------------------------------
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// This code is licensed to you under the terms of the GNU GPL, version 2 or,
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// at your option, any later version. See the LICENSE.txt file for the text of
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// the license.
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//-----------------------------------------------------------------------------
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// CRC16
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//-----------------------------------------------------------------------------
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#include "crc16.h"
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uint16_t update_crc16_ex( uint16_t crc, uint8_t c, uint16_t polynomial ) {
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uint16_t i, v, tmp = 0;
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v = (crc ^ c) & 0xff;
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for (i = 0; i < 8; i++) {
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if ( (tmp ^ v) & 1 )
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tmp = ( tmp >> 1 ) ^ polynomial;
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else
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tmp >>= 1;
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v >>= 1;
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}
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return ((crc >> 8) ^ tmp) & 0xffff;
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}
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uint16_t update_crc16( uint16_t crc, uint8_t c ) {
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return update_crc16_ex( crc, c, CRC16_POLY_CCITT);
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}
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// two ways.
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// msb or lsb loop.
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//
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uint16_t crc16(uint8_t const *d, int length, uint16_t remainder, uint16_t polynomial, bool refin, bool refout) {
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if (length == 0)
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return (~remainder);
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uint8_t c;
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for (uint32_t i = 0; i < length; ++i) {
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c = d[i];
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if (refin) c = reflect8(c);
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// xor in at msb
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remainder ^= (c << 8);
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// 8 iteration loop
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for (uint8_t j = 8; j; --j) {
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if (remainder & 0x8000) {
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remainder = (remainder << 1) ^ polynomial;
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} else {
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remainder <<= 1;
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}
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}
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/*
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c = (c ^ (uint8_t)(remainder & 0x00FF));
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c = (c ^ (c << 4));
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remainder = (remainder >> 8) ^ ((uint16_t) c << 8) ^ ((uint16_t) c << 3) ^ ((uint16_t) c >> 4);
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*/
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}
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if (refout)
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remainder = reflect16(remainder);
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return remainder;
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}
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uint16_t crc16_ccitt(uint8_t const *d, int n) {
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return crc16(d, n, 0xffff, CRC16_POLY_CCITT, false, false);
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}
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//poly=0x1021 init=0x0000 refin=true refout=true xorout=0x0000 name="KERMIT"
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uint16_t crc16_ccitt_kermit(uint8_t const *message, int length){
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return crc16_kermit(message, length);
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}
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uint16_t crc16_kermit(uint8_t const *d, int n) {
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return crc16(d, n, 0x0000, CRC16_POLY_CCITT, true, true);
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}
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//FeliCa uses XMODEM
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//poly=0x1021 init=0x0000 refin=false refout=false xorout=0x0000 name="XMODEM"
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uint16_t crc16_xmodem(uint8_t const *d, int n) {
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return crc16(d, n, 0x0000, CRC16_POLY_CCITT, false, false);
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}
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//ISO 15693 uses X-25, CRC_B (or 14443-3 )
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//poly=0x1021 init=0xffff refin=true refout=true xorout=0xffff name="X-25"
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uint16_t crc16_x25(uint8_t const *d, int n) {
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uint16_t crc = crc16(d, n, 0xffff, CRC16_POLY_CCITT, true, true);
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crc ^= 0xFFFF;
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return crc;
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}
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//CRC-A (14443-3)
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//poly=0x1021 init=0xc6c6 refin=true refout=true xorout=0x0000 name="CRC-A"
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uint16_t crc16_a(uint8_t const *d, int n) {
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return crc16(d, n, 0xc6c6, 0x1021, true, true);
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}
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bool check_crc16_ccitt(uint8_t const *d, int n) {
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if (n < 3) return false;
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uint16_t crc = crc16_ccitt(d, n - 2);
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if ((( crc & 0xff ) == d[n-2]) && (( crc >> 8 ) == d[n-1]))
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return true;
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return false;
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} |