Dictionary character limit?

[Tasselhoff]

If you know what the secret is, couldn't you just create a file with it appended to the string, and use something to work out the hash

Of course you can, but he tries to find the secret.

Yup, I edited. Depending on the character set used in the secret it could be a relatively quick operation to iterate through in bash. You could even break the set into separate scripts based on, say, the first character and run them in parallel. You wouldn't get the parallelism of a GPU, but the problem set is relatively small (e.g. 26^5 for lower case only, IIRC).