RC5
full spelling ： Rivest Cipher5
alias ： Ron's Code5
RC5 is a fast block cipher which has variable block size (32, 64 or 128 bits). It has a variable key size 0 to 2040 bits and a variable number of rounds (0 to 255). The RC5 has three routines; key expansion, encryption, and decryption. The exceptional simplicity is a notable feature in RC5 and its makes it easy to implement and analyze.
RSA Security, who have a patent on the algorithm, offer a series of US$10,000 prizes for breaking ciphertexts encrypted with RC5.
RC5 is designed by Ronald Rivest for RSA Data Security (now RSA Security) in 1994.