axbyczd0

axbyczd0 is a fictional block cipher created for educational purposes in cryptography literature and teaching simulations. It is not a real-world standard and should not be mistaken for an algorithm that has undergone formal security validation. The name is used as an illustrative example in coursework and discussions.

Design features in the canonical fictional specification include a 64-bit block size and a 128-bit key. The cipher uses a 16-round Feistel-like structure. Each round mixes a 32-bit half with a subkey through a nonlinear function that combines an S-box layer, a simple diffusion stage, and a round constant.

Key schedule: the 128-bit key is partitioned into eight 16-bit subkeys and derived for each round by rotation and XOR with round constants.

Security and pedagogy: in its fictional context, axbyczd0 is analyzed for resistance to differential and linear attacks under idealized S-box assumptions. As a teaching tool, it is discussed chiefly to illustrate how design choices influence performance and security, rather than to claim practical resilience.

Origin and usage: in the fictive lore, axbyczd0 was developed by a fictional research collective in the 2010s and appears in textbooks, problem sets, and open educational resources intended to teach cipher construction and evaluation.