yesterday I found some time and implemented RFC 6979 into python-ecdsa module.

RFC 6979 proposes algorithm of calculating 'k' value for signature from private key and signed data, so the 'k' is unique, but deterministic for every signature. This enabled simple unit tests of code using ECDSA signatures as well as some nice use cases for blackbox testing of 3rd party software (you can calculate on your own if some software is making valid signature, because there's no randomnes involved in the process). Yes, I'm referring Trezor :-).

There's pull request waiting for python-ecdsa author aproval: https://github.com/warner/python-ecdsa/pull/10

Aaand there's RFC 6979: tools.ietf.org/html/rfc6979

Thanks,

slush