NORTH ATLANTIC UNIVERSITY UNION
Data encryption standard was a main public encryption standard for more than 20 years, but now it is considered insecure. However, there are still numerous proposals of new lightweight cipher designs similar to DES, some of them only consisting of 4 Feistel rounds. It is known that there exist generic distinguishers for 4-round Feistel cipher, but their complexity scales exponentially with the cipher size. In the theoretical analysis, an ideal round function is considered. In this paper, the authors focus on a model of Feistel ciphers with design similar to DES.