tautcony / eac_logsigner

Transparent implementation of the EAC log checksum algorithm

EAC Log Signer

This is a transparent implementation of the Exact Audio Copy log checksum algorithm in C#. Includes an option to fix those pesky edited logs.

Installation

Download from the releases page and extract the zip file. Run the executable.

Usage

EAC Log Signer 1.0.0
Copyright (c) 2022 TautCony

  verify     Verify a log

  sign       Sign or fix an existing log

  help       Display more information on a specific command.

  version    Display version information.

Example

$ eac_logsigner sign bad.log good.log
$ eac_logsigner verify *.log
log1.log:  OK
log2.log:  OK
log3.log:  Malformed

Algorithm

1. Strip the log file of newlines and BOMs.
2. Cut off the existing signature block and (re-)encode the log text back into little-endian UTF-16
3. Encrypt the log file with Rijndael-256:
   • in CBC mode
   • with a 256-bit block size (most AES implementations hard-code a 128-bit block size)
   • all-zeroes IV
   • zero-padding
   • the hex key 9378716cf13e4265ae55338e940b376184da389e50647726b35f6f341ee3efd9
4. XOR together all of the resulting 256-bit ciphertext blocks. You can do it byte-by-byte, it doesn't matter in the end.
5. Output the little-endian representation of the above number, in uppercase hex.