Feistel algorithm is a design model from which many different block ciphers are derived. DES is just one example of a Feistel Cipher. A cryptographic system based on Feistel cipher structure uses the same algorithm for both encryption and decryption. In each round, the right half of the block, R, goes through unchanged. But the left half, L, goes through an operation that depends on R and the encryption key. In the proposed algorithm the left half L and the right half R both are goes through an operation depends on the round encryption key and L, R thus both L and R goes through changed in each round, this leads to possibility use one round only to encrypt/decrypt block of input data.
The second Kerckhoff's principle stated that a cryptographic system should be secure even if everything about the system, except the key, is public knowledge. virtually all the contemporary encryption algorithms such as DES, AES, etc. are applied this principle. This principle leads means that message depends solely on the security of the secret encryption key. The proposed algorithm designed according to this principle.
In modern era, cryptosystem needs to cater to users who are connected to the Internet. In such cases, using a secret algorithm is not feasible, hence Kerckhoff’s principles became essential guidelines for designing algorithms in modern cryptography
The Feistel algorithm, such as DES, in real implementation instead of using the whole encryption key during each round, a round-dependent key a subkey is derived from the encryption key. This means that each round uses a different key, although all these subkeys are related to the original key. But in the proposed algorithm each round subkey is independent and unrelated to another different subkeys, this making the proposed system stronger, more secure and makes it more difficult to attack.
The proposed algorithm design, both plaintext and ciphertext block size equal to 192-bit distributed over six groups of 32 bits for each and round subkey size of 176 bit (22 byte) for each round, because the left and right half of input block goes changed through an operation by apply two encrypting functions one for left half and the second for right half that takes two input for each, the round key K as well as R and L, hence the variable number of rounds from 1 and above possible to use.
Keywords: Block cipher, round, encryption, decryption, F-Function, Plaintext block, Ciphertext Block, Key Block, Symmetric