The TLS Handshaking Protocols

   TLS has three subprotocols that are used to allow peers to agree upon
   security parameters for the record layer, to authenticate themselves,
   to instantiate negotiated security parameters, and to report error
   conditions to each other.

   The Handshake Protocol is responsible for negotiating a session,
   which consists of the following items:
session identifier
      An arbitrary byte sequence chosen by the server to identify an
      active or resumable session state.

   peer certificate
      X509v3 [PKIX] certificate of the peer.  This element of the state
      may be null.

   compression method
      The algorithm used to compress data prior to encryption.

   cipher spec
      Specifies the pseudorandom function (PRF) used to generate keying
      material, the bulk data encryption algorithm (such as null, AES,
      etc.) and the MAC algorithm (such as HMAC-SHA1).  It also defines
      cryptographic attributes such as the mac_length.  (See Appendix
      A.6 for formal definition.)

   master secret
      48-byte secret shared between the client and server.

   is resumable
      A flag indicating whether the session can be used to initiate new
      connections.

   These items are then used to create security parameters for use by
   the record layer when protecting application data.  Many connections
   can be instantiated using the same session through the resumption
   feature of the TLS Handshake Protocol.