[Cryptography] Cryptography for consensual sex in California ?

[Henry Baker]

With California's new "yes means yes" law, how would you design a protocol for engaging in consensual sex, which would authenticate the parties' consents, which protected their privacy, but which couldn't be subsequently repudiated ?

This Good2Go app obviously doesn't satisfy any of these requirements, but it isn't so obvious how to design a protocol that would.

http://www.npr.org/blogs/thetwo-way/2014/09/29/352482932/california-enacts-yes-means-yes-law-defining-sexual-consent

http://www.slate.com/blogs/xx_factor/2014/09/29/good2go_a_new_app_for_consenting_to_sex.html