(Ron's Code or Rivest's Cipher algorithms) A family of secret-key cryptographic algorithms from RSA Security, Inc., Bedford, MA (www.rsa.com). Although RSA (formerly RSA Data Security and acquired by EMC in 2006) is widely known for its public key methods, its secret key algorithms are also widely used. Ronald Rivest is the "R" in RSA.Designed as a replacement for DES, RC2 uses a variable key and the block cipher method. RC4 uses a variable key and stream cipher method. Both RC5 and RC6 are block ciphers with variable keys up to 2,040 bits. RC6, designed by Rivest and others, uses integer multiplication for improved performance. RC6 was created to conform to the AES standard and was a finalist in the competition for the AES algorithm. See RSA, EMC, AES and DES.