Abstract: Cryptography is one of the important and useful technique in which usually a particular file is converted into unreadable format by using public key and private key system called as public key cryptosystem. Then as per the user requirement that file is send to another user for secure data or file transmission between original sender and receiver. In this transmission file of unreadable format is send, after receiving this file receiver used the similar algorithm technique and private key for getting the original file data. In this procedure various algorithms are used as a processing function and depending on that algorithm we used the private key. The power or strength of any algorithm is depending on the secret key used in sender client and receiver side client.

Keywords: Cryptography, authentication, Integrity, Confidentiality.