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,[2] so called bundles.[3] The term was introduced by Daemen and Rijmen in 2001.[1]
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).[2]