Improving Power System Information Security: Analysis of the Saturnin Cipher Algorithm

New power systems require efficient and secure communication technologies to facilitate information exchange between various devices and systems. Among these, encryption technology is key to ensuring communication security. The lightweight block cipher algorithm, Saturnin, is similar to the AES algorithm and maintains good security even in resource-limited environments. Therefore, it can be applied to various devices in the power system, such as smart meters, sensors, controllers, etc. An impossible differential analysis was conducted on the Saturnin algorithm to identify potential security vulnerabilities, thereby enhancing the security of the power system. Firstly, based on the structural characteristics of the Saturnin algorithm, sufficient conditions for the 3.5-round impossible differential distinguisher of the Saturnin algorithm were proposed and proven. Using these sufficient conditions, 64 distinguishers can be quickly constructed and divided into four categories. Secondly, these four categories of distinguishers can be extended forward by two rounds to obtain four attack paths. These four attack paths not only have the same plaintext structure but also have a large number of common key bits. By utilizing these two characteristics, the complexity of the attack scheme can be improved. Combining early plaintext death analysis techniques, a 5.5-round impossible differential attack scheme for the Saturnin algorithm was proposed. The data, storage, and time complexity are 2176.88 chosen plaintexts, 2143.88 algorithm scale, and 2176.91 times 5.5-round encryption respectively. This is currently a visible impossible differential attack scheme against the Saturnin algorithm.