A New Efficient Sbox for Strengthening PRESENT Like Block Ciphers Against Linear Cryptanalysis

Abstract

Substitution box(sbox) is the most crucial element in block ciphers like AES, PRESENT etc., in providing good security. Any weakness of sbox will lead to easier retrieval of secret keys. Cryptologists proved that PRESENT block cipher is vulnerable to linear cryptanalysis and main cause for the same is higher linear cardinality. In this paper we propose a new sbox in which Linear cardinality L Car equal to 2. The security strength of PRESENT block cipher (in which the original sbox is replaced by the proposed one) is evaluated through linear cryptanalysis. Also, the proposed sbox obtains a very good avelanche effect for the cipher. Minimum number of active sboxes and total bias of the cipher with proposed sbox are indications of higher security and performance. This sbox can be used for PRESENT like light weight block ciphers. Even though this paper is focused on security against Linear cryptanalysis, the proposed sbox shows excellent robustness against differential cryptanalysis also. The differential cardinality for the proposed sbox, D Car is also 2, which is a very good measure of security.