Rivest ciphers

Ron Rivest, an MIT professor and one of the founders of RSA Security, has devised a number of ciphers for that company, either alone or with collaborators. These designs are designated as RCn. Officially, "RC" stands for Rivest Cipher; it may also be taken as "Ron's Code".

RC4

RC4 is a very widely deployed stream cipher.

RC5

RC5 is a block cipher with 64-bit blocks, one of the DES generation of block ciphers. It was the first well-known cipher to make extensive use of data-dependent rotations to achieve nonlinearity. It is a Feistel cipher.

There is an RFC giving an RC5 specification for Internet use; see external links.

Its descendant RC6, also using data-dependent rotations, was an AES finalist. RSA Security have a page describing both ciphers; see external links.