A New Approach for Designing Cryptographic Systems based on Feistel Structure

Many Classical and modern cryptographic algorithms have been developed by the Cryptographers to facilitate data security operations. Classical ciphers are not being widely used because of limited key space. Public key cryptosystems are effective compare to symmetric systems but are slower than symmetric ciphers. Feistel Cipher structure is the reference structure for designing block- ciphers. In this paper we have proposed three variants to feistel structure to enhance the security of the data. The three constructive variants includes new design structure (The features of the derived structure includes 256 block length, processing of four parts of plaintext blocks, involvement of compression and padding operations), Generation of Round Key Using Random Number Generator approach and Use of unique round function for each round .Thus the existing Feistel structure has been modified to create a new block-cipher structure which incorporates effective key generation and round function approaches to provide effective data security.