Formats 0 to 3 are all suitable for use with the Triple Data Encryption Algorithm, as they correspond to its 64-bit block size. However the standard allows for other encryption algorithms with larger block sizes, e.g. the Advanced Encryption Standard has a block size of 128 bits. In such cases the PIN must be encoding into an extended PIN block, the format of which is defined in a 2015 amendment to ISO 9564-1.[2]