36 lines
1.1 KiB
Python
36 lines
1.1 KiB
Python
import sys
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import argparse
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from typing import List, Tuple
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def crc(data: List[int], len_: int, start_val: int, poly: int) -> int:
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crc_val = start_val
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for i in range(len_):
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crc_val ^= data[i]
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for _ in range(8):
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if (crc_val & 0x80) != 0:
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crc_val = ((crc_val << 1) ^ poly) & 0xFF
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else:
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crc_val <<= 1
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crc_val &= 0xFF
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return crc_val ^ 0xFF
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def main(data: List[List[int]]):
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for poly in range(0x01, 0xFF):
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for start in range(0x00, 0x100):
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found = 0
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for pkt in data:
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if crc(pkt[:7], 7, start, poly) == pkt[7]:
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found += 1
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if found >= 4:
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print(f"found = {found}! poly = {poly:02X} start = {start:02X}")
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if __name__ == "__main__":
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parser = argparse.ArgumentParser(description="CRC finder")
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parser.add_argument("data", nargs="+", help="Data packets (8-byte hex strings)")
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args = parser.parse_args()
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data = [list(bytes.fromhex(pkt)) for pkt in args.data]
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main(data)
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#thank you Alexey Esaulenko for original program design in CAN decoders |