US Patent 8726019 Context limited shared secret

In a communication system in which two communication entities seek to have a private or confidential communication session, a trust relationship needs first be established. The trust relationship is based on the determination of a shared secret which in turn is generated from contextual information. The contextual information can be derived from the circumstances surrounding the communication session. For example, the contextual information can include topological information, time-based information, and transactional information. The shared secret may be self-generated or received from a third party. In either event, the shared secret may be used as key material for any cryptographic protocol used between the communication entities.