RC4, RC5, RC6

RC4/RC5/RC6 is a series of symmetric encryption algorithms developed by RSA Security.

RC4 is a variable key-size stream cipher with byte-oriented operations. The algorithm is based on the use of a random permutation.

RC5 is a parameterized algorithm with a variable block size, a variable key size, and a variable number of rounds. Allowable choices for the block size are 32 bits (for experimentation and evaluation purposes only), 64 bits (for use a drop-in replacement for DES), and 128 bits. The number of rounds can range from 0 to 255, while the key can range from 0 bits to 2040 bits in size. RC5 has three routines: key expansion, encryption, and decryption.

RC6 is a block cipher based on RC5. RC6 is a parameterized algorithm where the block size, the key size, and the number of rounds are variable. The upper limit on the key size is 2040 bits. RC6 adds two features to RC5: the inclusion of integer multiplication and the use of four 4-bit working registers instead of RC5's two 2-bit registers.