Abstract:-The tremendous development in internet technology, wireless communication and the type of internet capable devices has increased the amount of network usage .Millions of users are associated with the network and thus there is need for network security. The sensitive data that is deposited and transmitted on the internet need protection from attackers and eavesdroppers who perform illegal actions. Cryptography algorithms are the key factor of the security mechanisms used for data storage and uninterrupted network transmissions. The data security purely depends on the Cryptography algorithm hence the keys must be managed in a good way. Security mechanisms are developed when a threat to security is identified. To identify the security risk associated with AES algorithm, a computational intelligence based approach for known cryptanalysis of Advanced Encryption Standard algorithm is introduced. Particle swarm optimization based cryptanalysis is used much now a days because of its fast convergence rate. A PSO oriented cryptanalysis technique for breaking the key used in advance encryption standard algorithm is introduced. This approach is for known cipher text-only attack for an AES encryption system, where the key is deduced in a minimum search space in contrast to the Brute Force Attack. The key used in AES can be detected effectively with Particle Swarm Optimization