Bricklayer function

{{Short description|Decomposable function in cryptography}}

File:AES-SubBytes.svg is a notable{{sfn|Weinmann|2009|p=36}} example of a bricklayer function: each 8-bit bundle of the 128-bit state is undergoing the same S-box transformation independently]]

In cryptography, the bricklayer function is a part of a round function that can be decomposed into identical independent Boolean operations on the partitioned pieces of its input data,{{sfn|Daemen|Rijmen|2013|p=22}} so called bundles.{{sfn|Daemen|Rijmen|2013|p=20}} The term was introduced by Daemen and Rijmen in 2001.{{sfn|Weinmann|2009|p=36}}

If the underlying function transforming the bundle is nonlinear, it is traditionally called an S-box. If the function is linear, Daemen and Rijmen use for it the term D-box (after diffusion).{{sfn|Daemen|Rijmen|2013|p=22}}