Broken key generation in Test.Shelley.Spec.Ledger.Utils

[mrBliss]

In Test.Shelley.Spec.Ledger.Utils, the mkGenKey, mkKeyPair, ..., functions, which use mkSeedFromWords are broken for some instantiations of crypto. I believe they work fine for mock crypto, which is what they're mostly used for, but not for all crypto, e.g., real crypto.

For example:

-- type DSIGN TPraosStandardCrypto = Ed25519DSIGN
> mkKeyPair @TPraosStandardCrypto (0, 0, 0, 0, 0)
(SignKeyEd25519DSIGN (SecretKey <scrubbed-bytes>),VKey (VerKeyEd25519DSIGN (PublicKey "*** Exception: SeedBytesExhausted {seedBytesSupplied = 16}

The problem is that some crypto algorithms need bigger seeds than mkSeedFromWords gives. mkSeedFromWords uses the MD5 algorithm to create hashes, which means these hashes are always 16 bytes. But Ed25519DSIGN needs a 32-byte seed.

The solution would be to use seedSizeDSIGN, seedSizeKES, seedSizeVRF, ..., to generate a seed of the right size, e.g., by repeating/concatenating/rehashing until the right size has been reached.

[JaredCorduan]

mkSeedFromWords is now hard coded to Blake2b_256