Need a lightweight sha1 module

I've been playing around with a small arduino and would like to see if I could get a websocket server working.

The only real obstacle is that as part of the handshake the browser sends a key, the server then adds "258EAFA5-E914-47DA-95CA-C5AB0DC85B11", creates an sha1 hash, encodes it in base64, then sends it back.

I've tried a couple of crypto libraries but they seem designed for the bigger arduinos that use client.h.

Any thoughts?