ABSTRACT
This chapter discusses the new algorithm entitled Extended HO-SAC has been introduced in which four IPVs have been complemented at a time. Substitution box or S-box in block ciphers is of utmost importance in public key cryptography from the initial days. A 4-bit S-box has been defined as a box of 16 elements varies from 0 to F in hex, arranged in a random manner as used in Data Encryption Standard or DES. In Linear Cryptanalysis of 4-bit crypto S-boxes, every 4-bit linear relations have been tested for a particular 4-bit crypto S-box. The presence of each 4-bit unique linear relation is checked by satisfaction of each of them for all 16 4-bit unique input bit patterns and corresponding 4-bit output bit patterns, generated from the index of each element and each element, respectively, of that particular crypto S-box. The concepts involved in cryptography and also some information on cryptanalysis had been provided to crypto-community in the late 1990s.
