AES has a fixed block size of 128 bits and a key size of 128, 192, or 256 bits, whereas Rijndael can be specified with block and key sizes in any multiple of 32 bits, with a minimum of 128 bits. The blocksize has a maximum of 256 bits, but the keysize has no theoretical maximum. AES operates on a 4×4 column-major order matrix of bytes, termed thestate (versions of Rijndael with a larger block size have additional columns in the state).