Differential Attack on IDEA Block Cipher Based on Its Key-Adding Function

This paper examines a new theoretical differential attack on the IDEA block cipher and several related ciphers from the same design family, such as PES and MESH. We present an analysis of the most probable differentials, which characterise the ciphers' security against the proposed attack. We also propose a design modification targeting the cipher's key-adding function to enhance its security against the attack.