Round Security and Super-Pseudorandomness of MISTY Type Structure

摘要

The security of an iterated block cipher heavily depends on its structure as well as each round function. Matsui showed that MISTY type structure is faster and more robust than Feistel structure in terms of its resistance against linear and differential cryptanalysis. On the other hand, Luby and Rackoff proved that the four round Feistel structure is super- Pseudorandom if each round function fi is a random function. This paper proves that the five round MISTY type structure is Super-pseudorandom. We also characterize its round security.