Folks: pycryptopp now does the two things that we need of it for the Small Distributed Mutable Files task -- RSA-PSS signatures and SHA-256 hashes. So I'm setting aside pycryptopp for the moment -- pycryptopp v0.2.1 works, as far as I know, and has reasonable unit tests: http://pypi.python.org/pypi/pycryptopp/0.2.1 Regards, Zooko