Message protection

Message protection is a term that describes the techniques used to ensure that a confidential message cannot be observed in transit, and cannot be illicitly changed.

The two aspects of message protection are:
Confidentiality
Protecting the message content from being intercepted
Integrity
Protecting a message from illicit modification

Confidentiality is achieved by encrypting the message (or parts of it) using a public key encryption scheme, so that only the intended recipient of the message can read it.

Integrity is achieved by digitally signing the message, so that the intended recipient can be confident that the message has not been changed illicitly.