From: marshmellow42 Date: Sat, 6 Jun 2015 02:39:56 +0000 (-0400) Subject: Modified kermit crc to use existing crc calc code X-Git-Tag: v2.1.0~4^2~1 X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/commitdiff_plain/07b5a3c3ba774ec93007827cf1233b4edb699bad Modified kermit crc to use existing crc calc code --- diff --git a/client/cmddata.c b/client/cmddata.c index e85b3a6c..cf105f88 100644 --- a/client/cmddata.c +++ b/client/cmddata.c @@ -1515,14 +1515,13 @@ int CmdFDXBdemodBI(const char *Cmd){ uint32_t crc16 = bytebits_to_byteLSBF(BitStream+64,16); uint32_t extended = bytebits_to_byteLSBF(BitStream+80,24); - uint64_t rawid = ((uint64_t)bytebits_to_byteLSBF(BitStream,32)<<32) | bytebits_to_byteLSBF(BitStream+32,32); + uint64_t rawid = ((uint64_t)bytebits_to_byte(BitStream,32)<<32) | bytebits_to_byte(BitStream+32,32); uint8_t raw[8]; num_to_bytes(rawid, 8, raw); - uint8_t *raw_ptr = SwapEndian64(raw, 8, 4); - if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(raw_ptr,8)); + if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(raw,8)); - uint16_t calcCrc = crc16_ccitt_kermit(raw_ptr, 8); + uint16_t calcCrc = crc16_ccitt_kermit(raw, 8); PrintAndLog("Animal ID: %04u-%012llu", countryCode, NationalCode); PrintAndLog("National Code: %012llu", NationalCode); PrintAndLog("CountryCode: %04u", countryCode); diff --git a/common/crc16.c b/common/crc16.c index d48df3b2..a37f1d7e 100644 --- a/common/crc16.c +++ b/common/crc16.c @@ -8,7 +8,6 @@ #include "crc16.h" - unsigned short update_crc16( unsigned short crc, unsigned char c ) { unsigned short i, v, tcrc = 0; @@ -44,16 +43,19 @@ uint16_t crc16_ccitt(uint8_t const *message, int length) { } uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) { - if (length == 0) return 0; - uint32_t crc = 0, q = 0; - uint8_t c; - - for (int i = 0; i < length; i++){ - c = message[i]; - q = (crc ^ c ) & 0xF; - crc = (crc >> 4) ^ (q * 0x1081); - q = (crc ^ (c >> 4)) & 0xF; - crc = (crc >> 4) ^ (q * 0x1081); - } - return crc; + return bit_reverse_uint16(crc16(message, length, 0x0000, 0x1021)); +} + +uint16_t bit_reverse_uint16 (uint16_t value) { + const uint16_t mask0 = 0x5555; + const uint16_t mask1 = 0x3333; + const uint16_t mask2 = 0x0F0F; + const uint16_t mask3 = 0x00FF; + + value = (((~mask0) & value) >> 1) | ((mask0 & value) << 1); + value = (((~mask1) & value) >> 2) | ((mask1 & value) << 2); + value = (((~mask2) & value) >> 4) | ((mask2 & value) << 4); + value = (((~mask3) & value) >> 8) | ((mask3 & value) << 8); + + return value; } diff --git a/common/crc16.h b/common/crc16.h index 3656ce27..8eb4befb 100644 --- a/common/crc16.h +++ b/common/crc16.h @@ -13,4 +13,5 @@ unsigned short update_crc16(unsigned short crc, unsigned char c); uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t polynomial); uint16_t crc16_ccitt(uint8_t const *message, int length); uint16_t crc16_ccitt_kermit(uint8_t const *message, int length); +uint16_t bit_reverse_uint16 (uint16_t value); #endif