"RC6 is an evolutionary improvement of RC5, designed to meet the
requirements of the Advanced Encryption Standard (AES). Like RC5,
RC6 makes essential use of data-dependent rotations. New features
of RC6 include the use of four working registers instead of two,
and the inclusion of integer multiplication as an additional primitive
operation. The use of multiplication greatly increases the diffusion
achieved per round, allowing for greater security, fewer rounds, and
increased throughput."