Q1 For DES encryption algorithm a Explain how Fiestel Ciphe

Q1: For DES encryption algorithm :-
a. Explain how Fiestel Cipher works
b. How is DES similar to Fiestel
c. How is 3DES different from DES
Q2: For AES encryption algorithm :-
a. Explain how it works
b. Compare AES with 3DES
c. which in your opinion is the best encryption algorithm and why?

Solution

1)

a)Feistel cipher is a symmetric structure used in the construction of block ciphers,in cryptography.here encryption and decryption operations are similar,just we have to reverse the key schedule .

b)DES IS the sub case of Fiestel.Both use same algorithm for encryption and decryption

c)

2

a)

AES is an iterative operation.. It comprises of a series of linked operations, some of which involve replacing inputs by specific outputs (substitutions) and others involve shuffling bits around (permutations).AES performs all its computations on bytes rather than bits. Hence, AES treats the 128 bits of a plaintext block as 16 bytes.

b)AES is the successor of DES as standard symmetric encryption algorithm for US federal organizations. ... DES uses 64 bit blocks, which poses some potential issues when encrypting several gigabytes of data with the same key. 3DES is a way to reuse DES implementations, by chaining three instances of DES with different key

c)AES data encryption is a more stronger elegant cryptographic algorithm, main strength lies in the option for various key lengths. AESallows you to choose a 128-bit, 192-bit or 256-bit key, making it exponentially stronger than the 56-bit key of DES.