Block cipher
One of the early block cipher designs was the Data Encryption Standard (DES), developed at IBM and published as a standard in 1977. A successor to DES, the Advanced Encryption Standard (AES); also using block cipher, was adopted in 2001. RC5 is a simple symmetric-key made by Ronald Rivest in 1994. RC6 is another made from RC5. RC stands for "Rivest Cipher", or alternatively, "Ron's Code".