w3c
Update for SPAKE2
This PR addresses Issue #235: Update SPAKE2 section according to current IETF draft
The IETF draft has had several updates since the SPAKE2 section was first written. I am taking this opportunity to align the protocol with the way the algorithm is written in the current draft, as an explicit two-round process.
By moving to a two-round process the auth-spake2-needs-psk message can be eliminated and replaced by having each agent explicitly state the PSK status in the auth-spake2-handshake message. This leads to a cleaner and easier to understand protocol.
In addition the message fields and associated text are updated to align with the terms used in the IETF draft.
Finally it updates the transcript-mac field to 64 bytes to allow the use of SHA-512 in the HMAC.
