Stanford Javascript Crypto Library

SJCL is secure. It uses the industry-standard AES algorithm at 128, 192 or 256 bits; the SHA256 hash function; the HMAC authentication code; the PBKDF2 password strengthener; and the CCM and OCB authenticated-encryption modes.

http://crypto.stanford.edu/sjcl/
https://github.com/bitwiseshiftleft/sjcl/tree/master/browserTest
http://bitwiseshiftleft.github.com/sjcl/demo/