Meysam Moradi - Department Of Computer Engineering, Hamedan Science And Research Branch, Islamic Azad University, Hamedan, Iran.
Hassan Khotanlou - Department Of Computer Engineering,Engineering Faculty, Bu-Ali Sina University, Hamedan, Iran.
Mahdi Abbasi - Department Of Computer Engineering, Engineering Faculty, Bu-Ali Sina University, Hamedan,Iran

From the emergence of cryptography up to now, strength of Encryption algorithms against attacks and threatens as an important issue has attracted a lot of attention. DES algorithm is a data encryption standard which is considered as a turning point in the history of cryptography. S -DES is the simplified version of Data Encryption Standard algorithm which is used for , investigation and education. In this study cryptanalysis is done on the strength of SDES encryption algorithm. In order to cryptanalyze, Decryption of plain data is studied through different crypt keys. SDES encryption algorithm with different data blocks was tested and the obtained results indicate that in different data blocks at SDES encryption algorithm, the plain data is decrypted using different crypt keys which is considered as a security problem for SDES encryption algorithm and cannot be an appropriate replacement for DES encryption algorithm in scale research , investigation and education.

Cryptanalysis, Simplified Data Encryption Standard, Crypt Key, Plain Data, Cipher Data.