Structural Analysis based on Integral Characteristic of a Reduced Round Block Cipher with Making an Improvement

In symmetric encryption, block ciphers are more important than stream ciphers, message authentication codes and authenticated encryption schemes, because they are often used as the secure building blocks of other types. Structural analysis is one of the block ciphers cryptanalysis methods which performs attacks without prior knowledge of their internal operators such as permutations and s-boxes. In this paper, using a known 4-rounds integral distinguisher on AES, for the first time, two integral attacks are made on a new native block cipher with a 256-bit key and block length. These attacks, are made on 1-round and 2-rounds of this 3-rounds block cipher due to the weaknesses of the round function. The memory, data, and time  complexities of the best attack in this article are 232 bytes, 2128 plaintexts and 2206 encryption operations. Given the key's length, the complexity of the attack is less than the complexity of the comprehensive search key space attack (2256) and therefore it is an effective shortcut attack. In addition, some recommendations are made to improve this native cipher.