Once a context is established, the two principals can exchange data across the network in a secure fashion. Data origin authentication and integrity checks may be applied to the message so that the acceptor can verify the origin of the message and detect if the message was modified while in transit. This is called message integrity. In addition, the data may be encrypted such that only the acceptor can decrypt and make sense of it. This is called message confidentiality.
Some mechanisms offer applications fine control over how message protection is done.
Honoring these requests, separately or in combination, depends on the underlying mechanism. A context token is exchanged during context establishment, and a message token is used over an established context to provide per-message protection. A principal acquires credentials as proof of identity when communicating with a peer. The initiating principal authenticates itself to the acceptor. The initiator may optionally request mutual authentication, in which case the acceptor in turn authenticates itself to the initiator.