1 Introduction
1.3 Security services

A security service is a service that ensures adequate security of the systems or of data transfers. Security services are implemented by security mechanisms according to security policies.

For over twenty years, information security has held confidentiality, integrity and availability (known as the CIA triad) to be the core principles of information security. Later, other elements of information security were added to the three classic security attributes of the CIA triad. These elements are authentication, access control, non-repudiation, and privacy. Nevertheless, this classification is subject of debate among security professionals.