The current default authentication method in TypePad and Movable Type's Atom implementation is WSSE. WSSE is a header containing a token based on username, password and date and looks like: X-WSSE: UsernameToken Username="name", PasswordDigest="digest", Created="timestamp", Nonce="nonce" I have implented a library in JavaScript to generate this header, quite useful for XmlHttpRequest and GM_XmlHtt