website/docs/MPC/_tls_handshake.md

TLS handshake

During the TLS handshake the TLS Client and the TLS Server compute the session keys needed to perform the encryption and decryption of data.

In TLSNotary protocol User and Notary jointly play the role of the TLS Client. They use MPC to compute the session keys in such a way that neither party ever learns the full keys but each has their share of the keys.

First they compute their shares of the TLS Client's ECDH secret using this protocol. Since an ECDH secret is an EC point, the parties have their shares of that point.

Then they compute their shares of the pre-master secret (PMS) using an MPC protocol described here.

Then the parties input their PMS shares as private inputs to the DEAP protocol (along with some other public data). They perform the following in MPC:

• they derive their shares of the TLS session keys
• they encrypt the Client Finished message (and the User sends the CF to the server)
• (the User receives the Server Finished message from the server and) they decrypt the SF message and check its authenticity.