Why not add the ability to search by ripemd160 or known public key to speed up 
And which bitcrack version supports random key space function ?
And which bitcrack version supports random key space function ?
From a cursory look at the source, it appears that it uses ripemd160 internally, converting from base58 at init, so that speed optimization is already done.
Matching against pubkey would be handy (if it doesn't already do this?)
Why would you want to search random key space?