I know this would be less fun, but given that the key space was only 36^4, why not just run the actual decryption functionality in QText? Like, even if it takes 1 second to decrypt, spin up 32 cores and wait a day. They allude to the idea that checking the key derivation is faster, but I wonder by how much.
(of course, it’s still interesting to read about 90s encryption, so I appreciate that they did it the fun way)
I assume the hard part would have been automating this or extracting the key derivation and check code out of QText so you can run it separately in a loop.
I'm pretty sure you can automate DOSBox input, but if you're more comfortable with reversing algorithms than writing reliable UI automation script then what they did isn't necessarily an overkill.
(of course, it’s still interesting to read about 90s encryption, so I appreciate that they did it the fun way)