Reconstruction of s2DES S-boxes and their Immunity to Differential Cryptanalysis
Kwangjo Kim, S Park, S Lee · 1993
At Crypto'92, L.R. Knudsen[7] showed that s²DES is insufficient to assure against differential attack. In this paper, we propose a provable design criterion to strengthen s²DES against differential attack without disturbing its cryptographic structure. We show that new s²DES S-boxes can be constructed with our new design criteria and suggest new 8 s²DES S-boxes for replacing the current DES S-boxes. Simply called this algorithm as s³DES, the result of our estimation and Knudsen's recent analysis [9] give us that s³DES can resist against differential attack better than DES and s²DES, i.e., breaking s³DES by differential attack is less efficient than key-exhaustive search.