Ballet128 分组密码的不可能差分分析

The block cipher Ballet is one of the winning algorithms of the National Cryptographic Algorithm Design Competition. It employs the ARX structure and has three versions, namely, Ballet128-128, Ballet128-256, and Ballet256-256. In its impossible differential cryptanalysis, currently there are only 7-round impossible differential characteristics provided by the designers. This study reassesses the impossible differential security of the Ballet128 cipher. By employing proof methods, 8-round impossible differentials of Ballet128 is established. By utilizing the characteristics of key XOR operations and data shifting within the Ballet round function, an equivalent structure for Ballet128 is constructed. Building upon this foundation, the distinctive features of the equivalent structure are utilized to devise impossible differentials attacks on 11-round Ballet128-128 and 13-round Ballet128-256. The 8-round impossible differential characteristics are the longest impossible differential characteristics for the Ballet128 cipher to date.