Blokcipher

Blokcipher is a generic term used in cryptography to denote a hypothetical or pedagogical block cipher. It is not a specific, standardized algorithm. The name combines “block” and “cipher” with a stylized spelling and is commonly employed in educational materials to illustrate design choices, security analyses, and comparative discussions without tying them to a real-world specification.

In typical discussions, a blokcipher is assumed to be a symmetric-key algorithm that operates on fixed-size blocks, often 128 bits, and uses a master key of variable length (for example 128, 192, or 256 bits). The design is described in terms of a round function and a key schedule that derives round keys. Internally, blokciphers are presented either as substitution-permutation networks or as Feistel networks, with multiple rounds that provide nonlinear substitutions, diffusion, and key mixing.

Security considerations for blokcipher focus on theoretical resistance to standard cryptanalytic models. Analyses may explore differential and linear cryptanalysis in idealized settings, as well as the impact of related-key models and key-schedule weaknesses. Since blokcipher is not a concrete instantiation, security claims depend on the hypothetical construction rather than on real-world implementation details.

Modes of operation for blokcipher follow the same principles as real block ciphers. To encrypt data streams, modes such as CBC, CFB, OFB, or CTR are applied, with careful management of padding and nonces to maintain confidentiality in practice. Overall, blokcipher serves as a teaching tool rather than a deployed cryptographic standard, and it is not used in official security protocols.