Known-ciphertext cryptanalysis approach for the Data Encryption Standard technique

In this paper, we present an approach for the cryptanalysis of four-rounded Data Encryption Standard (DES) based on particle swarm optimization (PSO). It is actually a known ciphertext only attack that aims at deducing optimum keys depending upon their fitness values. The approach finds the best keys through a fitness function called N-gram statistics. The results indicate that the proposed approach is efficient in finding missing key bits of the data encryption standard algorithm.