Microsoft research has published a JavaScript library that extends the W3C WebCrypto API.

http://research.microsoft.com/en-us/downloads/29f9385d-da4c-479a-b2ea-2a7bb335d727/default.aspx

The download is amazingly big for a JavaScript library: 254 MB!

I’ll have a look over the source. If you are interested in security and JavaScript you should too.