Covert Channels in SSL Session Negotiation Headers

The Handshake headers of the SSL/TLS protocol contain several multi-byte random data fields used in the generation of the encryption keys used during the session. This random data can be replaced with covert messages that can be intercepted on the wire using packet capture techniques. By encoding data into these fields, a modified SSL client can send messages to a legitimate destination, with legitimate application payload data and still leak covert messages to a receiver listening on the wire.