Research On Security Of Block Cipher SMS4

With the development of wireless networks, wireless network security has also become the focus of attention of the society, as is now widely used in domestic WAPI (Wireless Authentication Privacy Infrastructure) wireless networking standard, also be-come in recent years a password using the encryption algorithm SMS4analysis where the hot spots. SMS4algorithm is iterative unbalanced Feistel structure of a32block encryption algorithm key length and packet length is128. The encryption algorithm and decryption algorithm is exactly the same, except that the decryption key is reverse obtained by the encryption key. For the the SMS4algorithm’s key expansion algorith-m, just change some parameters in the linear encryption algorithm L transform and round function obtained.Given the historical significance and importance of WAPI SMS4algorithm pub-lished after they get the password academic extensive attention, multi-staff also pro-posed a variety of attacks for SMS4block cipher algorithm. The most efficient attack was raised in2008by such as T.Kim and J.Kim, people, a rectangle attack, an attack by16rectangular case, constructed18SMS4algorithm rectangle attack.[9] found a12impossible differential path on16SMS4algorithm impossible differential attacks. This article draws on various methods before, meet in the middle, found a14impossi-ble differential path impossible differential attack on18SMS4algorithm, and get better results.The SMS4is the first commercial block cipher published by Chinese governmen-t.It’s a32-round block cipher encrypted by128-bit keys.By analyzing the changes of the difference between input and output pairs in each round, this paper presents a new impossible differential path of the14-round SMS4. Using this path, a new method is submitted to cryptanalyze an18-round SMS4.The time complexity of the attack is2117.06partial encryptions.