University of Technology-IraqEngineering and Technology Journal1681-690031120130128New Approach for Modifying DES Algorithm by Using Multiple Keys Depend on Heuristic Search Algorithmطريقة جديدة لتحسين خوارزمية التشفير DES باستخدام المفاتيح المتعددة بالاعتماد على خوارزمية البحث الموجه789283954ENAlaa K. FarhanSuhad M.KadhemNoor MonemDena SaadJournal Article20130101In this paper, artificial search algorithm(breath algorithm ) are used to design a symmetric key cryptography system based on DES algorithm,the LFSRs and breath algorithm are applied to generate a pseudo-random numbers sequence (PNS) which is used during the encryption process. The quality of PNSs highly depends on the set of LFSRs rule by selected the polynomial equation cells . This paper introduces a new method to enhance the performance of the Data Encryption Standard (DES) Algorithm. This is done by building a new structure for the 16 rounds in the original algorithm. This structure makes use of multiple secrete keys and the length of key is256-bits to process one block 256-bits of plain text.https://etj.uotechnology.edu.iq/article_83954_b5866cc621c9098820ba2c8ab30231d1.pdf