Known-plaintext attack of DES-16 using Particle Swarm Optimization

Discovering the root key bits in the cryptanalysis of 16-rounded Data Encryption Standard (DES-160) is considered to be a hard problem. In this paper we present an approach for cryptanalysis of DES-16 based on Particle Swarm Optimization (PSO) using Known-plaintext attack and some equations that deduced from the relationship between sub-key differences and root key information. In Known-plaintext attack the cryptanalyst possesses one or more plaintext/cipher text pairs formed with the secret key and attempts to deduce the root key that used to produce this cipher text. In our approach, PSO is used as optimization technique to collect the optimal effective plaintexts from a plaintext search space according to the proposed fitness function then the set of collected plaintexts and the corresponding cipher texts used to extract the best eight sub-key differences from which most bits of the root key are discovered.