1. An apparatus comprising: a key-based block cipher circuit, the block cipher circuit configured to encrypt a data block based on a key; wherein the block cipher circuit comprises a plurality of round circuits that are arranged in a pipelined sequence of operatively adjacent round circuits, the round circuits for simultaneously performing rounds of encryption; and wherein the block cipher circuit is run-time scalable with respect to how many of the round circuits are active and how many passes through the round circuits are needed to encrypt a data block.