Abstract :
In data communication,the aspect of security and confidentiality data is needed. To maintain the security and confidentiality of the data is by using cryptography. Cryptography is the science of mathematical techniques related to aspects of information security such as data confidentiality, data authenticity, data integrity, and authentication data. Text security is done by a hybrid cryptography in a text file that is first performed using ADFGVX Cipher encryption, then the results of ADFGVX Cipher encryption is encrypted using the RSA. Testing primes using the Fermat algorithm. Implementation of the system using C# programming language in Microsoft Visual Studio 2010. The system on RSA was tested with a maximum key length of 256 bits to 32 bits intervals. The results showed that RSA method has the fastest time during the process of encryption the decryption process.