Score:1

Is there any known/standard encoding or cipher method that uses a 64-character alphabet from byte 30 (ASCII `0`) to byte 6F (ASCII `o`)?

cn flag

Is there any known/standard encoding or cipher method that uses a 64-character alphabet from byte 30 (ASCII 0) to byte 6F (ASCII o)?

I'm trying to reverse-engineer a file format, and I have good idea of what some of the contents of the files should contain, but I'm not seeing any obvious patterns in the data that correspond to my expectations. The biggest peculiarity that I've been able to identify is the fact that the bytes are limited to this range (other than 4 FF bytes that begin every file). It's not Base64, Ascii85, or uuencoding, as far as I can tell.

If it helps, the byte distribution across the 152 files I have has 30 (ASCII 0) as far and away the most common, followed by 45 (ASCII E) and 55 (ASCII U); 4B, 6E, and 4A (ASCII K, n, and J) are least common. The file format dates back to circa 2000.

I'm wary to post actual examples of the data, as I don't know if the files contain any sensitive materials, but I can easily test hypotheses should they arise.

kelalaka avatar
in flag
This better suits https://reverseengineering.stackexchange.com/
poncho avatar
my flag
My guess is that it's a simple encoding of 6 bits (adding 0x30); I would have no idea how they map 8->6 bits (or even if they do - it's possible that the original data was 6 bits)
Daniel S avatar
ru flag
It sounds a bit like [uuencoding](https://en.wikipedia.org/wiki/Uuencoding) Unix-Unix encoding, but the range is different.
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