0

Does anyone recognize a pattern in these checkusms/CRCs, etc? The data of interest always falls in the range of ASCII characters, and is always the same length:UD1809T6587300000YBT03/02/18 Here is an example of the complete message:

69 27 FB 3A (checksum/CRC?)
A0 0F 97 0F B6 37 F4 2C (these never change)
65 BB 67 AE 1C BD 72 DC (these never change)
D9 3F B4 D2 7F BC D3 BA (these never change)
5D 39 00 9D 0B BA 35 63 (these never change)
UD133110281600000YBT500000007/31/13 (the ASCII data)
BB 19   (checksum/CRC?)

I have 3 messages where only one digit of the serial number changes:

UD133110281600000YBT500000007/31/13
UD133110281700000YBT500000007/31/13
UD133110281800000YBT500000007/31/13

Here are the leading and following checksums for this data:

69  27  FB  3A      BB  19
68  17  00  3B      B1  18
13  F1  00  3B      37  19

The last byte of the leading group is always either 3A or 3B. The last byte of the trailing group is always either 18, 19, or 1A

Can anyone help me narrow this down as to what kind of error checking this might be? Below are 50 samples of the checksums:

EF  5B  F7  3A      6C  1A
54  35  F6  3A      AB  19
00  F6  F5  3A      02  1B
5A  1D  F9  3A      A1  19
EA  1E  FC  3A      2F  1A
15  FE  04  3B      57  19
52  04  06  3B      97  18
A3  1D  03  3B      FC  18
00  70  FD  3A      87  1A
4F  FF  00  3B      93  19
D1  20  FE  3A      3E  1A
01  3D  03  3B      72  18
4D  80  04  3B      16  19
72  B8  F8  3A      52  1A
32  A1  00  3B      10  19
A5  3E  FA  3A      06  1A
BD  A7  F8  3A      8D  1A
A1  2B  05  3B      00  19
98  A0  0A  3B      75  19
07  43  FB  3A      79  19
09  59  FC  3A      95  19
A5  2C  08  3B      03  19
99  4E  02  3B      1C  19
1C  D7  00  3B      28  19
7A  4D  FB  3A      EE  19
8F  52  01  3B      13  19
25  48  03  3B      B4  18
AA  53  01  3B      42  19
04  2D  F6  3A      6F  19
1B  11  03  3B      63  18
B0  78  F9  3A      5A  1A
21  D6  F9  3A      1B  1A
BB  16  FD  3A      00  1A
00  47  01  3B      65  19
6C  DA  F6  3A      68  1A
27  C8  01  3B      1F  19
9D  54  04  3B      15  19
Robertjf
  • 1
  • Try xoring two of the three patterns that differ by one serial number. Do this for all three combinations, 1+2, 1+3, 2+3. This will result in 3 patterns that are mostly zeros. If this is CRC or RS, you should get a "valid" result, and it will be easier to figure it out. Note that if this is a CRC that is post complemented (xorout = 0xffff), then the xor of two patterns will result in a non complemented CRC, which may also help. – rcgldr Dec 05 '18 at 13:54
  • Only your first, second, and second-to-last bytes look like they could possibly be parts of CRCs. Any decent CRC will look effectively like random data even with just single bit changes in the message. – Mark Adler Dec 05 '18 at 22:51

0 Answers0