AES-128 Sbox - Rom Issue

Thank you both for your replies - very much appreciated.

My main issue with using a Synchronous ROM is as follows...

My design uses a FSM, having 13 states - and on each clock cycle the state is increased (generally speaking, in each state, 1 round of encryption/decryption is performed). When using an array, thus the LUT's the instruction...

for (shortint c = 0; c < 4; c++) begin

State[r][c] = Sbox[State[r][c] >> 4][State[r][c] & 8'h0f];

end

Would carry out all 4 substitutions within a single clock cycle, however by using a ROM that piece itself would take 4 clock cycles.

How would I synchronise my current FSM using a ROM - would I have to increment states every X clock cycles instead of every 1?