NobleSir has published a whitepaper on confidential transactions on github
with an ongoing discussion at /r/monero
very interesting read for especially everyone looking forward to zerocash implementations, since it combines the benefits of zc with the monero inherent auditing possibility.
a little update: according to the lead cryptographer on this topic(Shen Noether) his work is probably going to be finished within in the next days.
check the stickied reddit thread: https://www.reddit.com/r/Monero/comment ... _versions/
this is means, that zerocash is most likely not going to be the first currency with confidential transactions. ignoring the fact that zercash is only vaporware right now.
monero has taken the lead again!