5.1.1 Cryptography

Cryptography is the mathematical foundation of information security. It encompasses the principles, means, and methods used to transform information to protect its confidentiality, integrity, and authenticity. Cryptography provides mechanisms for achieving many of the services defined above—confidentiality through encryption, integrity assurance through cryptographic hashing, authentication through digital signatures and message authentication codes (MACs), and non-repudiation through public-key infrastructures (PKI) and certificate-based identity validation.

In practice, cryptography is divided into two main branches:

Symmetric cryptography, in which a shared secret key is used for both encryption and decryption.
Asymmetric (public-key) cryptography, in which mathematically related key pairs enable secure key exchange, authentication, and digital signatures.

Together, these techniques form the basis for secure communication protocols, data protection, and trust management across modern networked systems.