A problem with sending a hash of the URL, is that you cannot canonicalize the URL on the server side anymore. A simple example: the hash of "http://www.foo.com/

A problem with sending a hash of the URL, is that you cannot canonicalize the URL on the server side anymore. A simple example: the hash of "http://www.foo.com/bar/ http://www.foo.com/bar/ would differ from the hash of "http://www.foo.com/bar http://www.foo.com/bar. I guess you could do some canonicalization on the client-side, though...