Triple DES was the next enhancement to DES. It concatenates DES ciphertext with itself and uses up to three key, hence the name. the Advanced Encryption Standard (AES) has now replaced DES and Triple DES as the new U.S. federal government standaed. AES (which is actually the Rijndael algorithm) is a cipher block algorithm that uses a 128-bit,192-bit, o 256-bot block size and key size of 128 bits. Other examples of block cophers are RSA's RC2 and RC5, Entrust's CAST, and Counterpane Systems' Blowfish. Unlike DES, they can use variable-sized, large keys. For these algorithms, a larger key size results in stronger encryption. Cryptographers will continue to recommend ever-increasing key size for these encryption techniques, as computing power catches up to the complexity of the algorithms.