Protocol

A security protocol (cryptographic protocol or encryption protocol) is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods, often as sequences of cryptographic primitives. A protocol describes how the algorithms should be used. A sufficiently detailed protocol includes details about data structures and representations, at which point it can be used to implement multiple, interoperable versions of a program.

Cryptographic protocols are widely used for secure application-level data transport. A cryptographic protocol usually incorporates at least some of these aspects:

• Key agreement or establishment
• Entity authentication
• Symmetric encryption and message authentication material construction
• Secured application-level data transport
• Non-repudiation methods
• Secret sharing methods
• Secure multi-party computation

For example, Transport Layer Security (TLS) is a cryptographic protocol that is used to secure web (HTTP/HTTPS) connections.¹