Abstract: Today, it is important that information is sent confidentially over the network without fear of hackers or unauthorized access to it. Cryptography was created as a technique for securing the secrecy of communication and many different methods have been developed to encrypt and decrypt data file in order to keep the message secret. Cryptanalysis on symmetric key cryptography is encouraging the use of larger key size and complex algorithm to achieve an unbreakable state. To implement this system AES (Advanced Encryption Standard) and CBC (Cipher Block Chaining) algorithms are used. Data transfer system can prevent from interruption, destruction reparation of eavesdroppers, hacker, and blockers and so on, and can make the data secure. The implementation is written in C# using Microsoft Visual Studio 2008 and Microsoft. Net Framework v3.5.