Substitution–permutation network

A Substitution-Permutation Network (SPN) is a type of symmetric key cipher used for the encryption and decryption of data. It combines two fundamental operations: substitution, which alters the bits in a specified manner, and permutation, which rearranges those bits. This approach is integral to many modern block ciphers and is designed to provide strong security properties through diffusion and confusion. ### Key Components of a Substitution-Permutation Network 1.