A processing system includes a memory and a cryptographic accelerator operatively coupled to the memory. The cryptographic accelerator performs a split substitute byte operation within two paths of a cryptographic round by determining a first output from a first path by applying a mapped affine transformation to an input bit sequence represented by an element of a composite field of a finite-prime field, wherein the first output is represented by a first element of the composite field of the finite-prime field, and a second output from a second path by applying a scaled mapped affine transformation to the input bit sequence, wherein the second output is represented by a second element of the composite field and is equal to a multiple of the first output in the composite field.