An optimized key scheduling algorithm for CAST-128 using dynamic substitution S-box

Abstract

An optimized key scheduling algorithm for the 64-bit block cipher CAST-128 by using dynamically substituting of S-box. In this regard, an attempt has been made to modify key scheduling algorithm for generating subkeys of a secret-key block cipher which is CAST-128 algorithm so as to enhance performance by modifying the generation of subkeys using dynamic substitution of S-box. The CAST-128 uses four static substitution of S-box to generate subkeys, where as the proposed structure generates subkeys using substitution of S-box dynamically to provides the performance of CAST-128. The approach considers different security aspects and metrics evaluation for verification.