Breaking A Playfair Cipher Using Memetic Algorithm

The playfair cipher operates on pairs of letters. The cipher text is broken into group of blocks, each block contains two letters. Encryption and decryption cipher depends on key search, which is a square matrix that contains 5x5 letters. The matrix contains every letter expect letter j. In this paper the cryptanalyst a playfair is presented using search techniques. It is a Memetic Algorithm, another method is used to know a key through a correct Digram letters, which is used as an essential factor in the cryptanalyst cipher text. Results without memtiec algorithm and with it have been compared, to see which one has a best solution. The result clears that the memetic algorithm has a best solution more than a classical method, and faster than without used it, which has optimal solution. The length of text is 1802 letter. The key size is 25 letters as a matrix 5x5. All the algorithms were programmed using Matlab programming as M-file, and tested successfully Keyword: Playfair Cipher, Frequency of Bi-Grams, cryptography, Memetic Aalgorithm (MA), And Key Space. ةرفش لیلحت Playfair ثحبلا ةیمزراوخ مادختساب MA م . م دومح نسحملا دبع للاد ةینورتكللااو ةیئابرھكلا تاینقتلا ةیلك ينقتلا میلعتلا ةئیھ ةصلاخلا : ـلا ةرفش لمعت playfair فرحلأا نم جوز ىلع . لاغ صنلا مسقی ى كولب لك يوتحی ،تاكولبلا نم ةعومجم رحلأا نم جوز ىلع ف . فرحلأا نم ةعبرم ةفوفصم لكش ىلع نوكی ثیح ،ثحبلا حاتفم ىلع ریفشتلا كفو ریفشتلا ةیلمع دمتعت 5x5 . Journal of Engineering and Development, Vol. 17, No.5, November 2013 , ISSN 18137822 173 ـلا ةرفش لیلحت مادختسا مت ثحبلا اذه يف playfair يهو ثحبلا تایمزراوخ تاینقت نم ةینقت مادختساب memetic Algorithm ع تدنتسا ىرخأ ةقیرط تمدختساو ، ةغللا يف اعویش رثكلأا ةجودزملا فورحلا راركت ىل ةرفشلا لیلحت يف يساسأ لماعك مدختسی ثیح ،ةیزیلكنلاا . ةیمزراوخلا مادختساب جئاتنلا هنراقم مت memetic Algorithm جئاتنلا ترهظأ ثیح ،اهمادختسا نودبو ورعملا ةیكیسلاكلا ةقیرطلا نم لادب ةیمزراوخلا مادختسا ةعرس ةف . فدهت memetic Algorithm كلتمت ثیح ، لیلق تقوبو لثملأا لحلا . صنلا لوط 1802 فرح . جمانربب اهتجمرب تمتو تایمزراوخلا تقبط MATLAB حاجنب