What is RC6?
Q: What is RC6?
A: RC6 is a symmetric-key block cipher derived from RC5. It is a parameterized algorithm with a variable block size, key size, and number of rounds.
Q: Who designed RC6?
A: RC6 was designed by Ron Rivest, Matt Robshaw, Ray Sidney, and Yiqun Lisa Yin.
Q: What are the default block sizes for RC5 and AES?
A: The default block size of RC5 is 64 bits while the default block size of AES is 128 bits.
Q: How does the structure of RC6 compare to that of RC5?
A: The structure of RC6 is very similar to that of RC5 but it uses an extra multiplication operation not present in the latter as well as four b/4-bit working registers instead of two b/2-bit registers.
Q: Why are four working registers used instead of two in order to build the AES architecture using only 32-bit operations?
A: Integer multiplication is used to increase diffusion achieved per round so fewer rounds are needed and speed can be increased. Four working registers are required because 32-bit operations are used when dealing with 64-bit blocks and 64-bit operations when dealing with 128-bit blocks.
Q: Is there any licensing or royalty payments required for products using the algorithm?
A: Yes, since it's a proprietary and patented algorithm (by RSA Security U.S. Patent 5,724,428 and U.S. Patent 5,835,600 ), licensing and royalty payments may be required for any products using the algorithm.
