S-box

Tags

cryptography

Is a [see page 26, box] used in a cryptographic system which performs the role of substitution cipher. It replaces one block of bits with another block, that could contain a different number of 0s or 1s than the input block.

A substitution box can be seen as a very simple block cipher.

These are often implemented as a [see page 3, lookup-table], an exhaustive list of possible inputs with possible outputs, however for suitably large S-Boxes this quickly becomes infeasible. In these situations we instead algorithmically calculate the output using some function.