1. Apparatus for generating round-key words in accordance with a Rijndael algorithm, the apparatus comprising: (a) a key expansion register block (e.g., 401 ) comprising a key expansion register (e.g., 411 ) adapted to receive a final cipher key of a key expansion schedule in accordance with the Rijndael algorithm, wherein the key expansion register block is adapted to shift the contents of the key expansion register; (b) a round constant generator (e.g., 402 ) adapted to generate a current round constant (e.g., 402 a ) based on a seed value and in response to a first control signal (e.g., COL_ 1 ); (c) a first XOR adder (e.g., 404 ) adapted to add a first word (e.g., w[ 0 ]) of the key expansion register to a second word (e.g., w[ 1 ]) to generate and provide a first sum (e.g., 404 a ) to the key expansion register block, wherein: the first word of the key expansion register is a round-key word provided as an output (e.g., 103 b ) of the apparatus; and the first sum comprises a first-sum first byte (e.g., 404 a [ 7 : 0 ]), a first-sum second byte (e.g., 404 a [ 15 : 8 ]), a first-sum third byte (e.g., 404 a [ 23 : 16 ]), and a first-sum fourth byte (e.g., 404 a [ 31 : 24 ]); (d) a transformation block (e.g., 403 ) adapted to generate a transformed word (e.g., 422 a ) based on the first sum and the current round constant over four counts of a first cyclical counter (e.g., 102 c ); and (e) a second XOR adder (e.g., 405 ) adapted to add the transformed word to the first word of the key expansion register to generate and provide a second sum (e.g., 405 a ) to the key expansion register block.