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Do you still have that bruteforce code? I've been trying on and off to reverse engineer the RS ECC in Chirp, a (now discontinued) app for sharing tokens over speaker/microphone.

My current progress is summarised in https://math.stackexchange.com/questions/663643/discover-par... and https://github.com/moreati/chirppy/blob/master/trials.py

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A few references I've found suggest that is RS(9,5) and might not actually be using GF(32); although you have 18 "symbols" of 90 bits total, with 50 bits of data and 40 parity, I doubt those are the actual RS symbols.

In fact, those parameters line up with 9 * 10-bit symbols in each block, 5 10-bit data and 4 10-bit ECC. I would try a shortened RS(1023,1019) in GF(1023), taking pairs of the 5-bit "symbols".

Here is the code I originally used. I was bruteforcing a non-shortened RS(511,503) in GF(511) which had a somewhat complex transformation between bytes and symbols, fortunately partly documented at the time:

http://pastebin.com/6nK2GSBh (partly anonymised. public domain.)

Something else you may find useful, more Python code for bruteforcing RS parameters:

https://en.wikiversity.org/wiki/Reed%E2%80%93Solomon_codes_f...

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