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Cryptography is the art of communicating secretly, Privately.
The word is derived from Greek words, where “Krypto” means “hidden” and “grafo” means “write”.In olden days Cryptography was used in deciding on the war plans at the borders. This was to maintain secret ways to attack enemies without speaking a word. They made signs and symbols with hands and legs to pass on the information uniquely, so that the enemies could not understand their sign language.

Now, Cryptography is used in communications through computers and networks. The information or message to be passed by a sender is converted in to an incompatible form, which could not be understood by others. This information is now transferred through networks and at the receiving side the incompatible text is converted in to compatible information that could be understood. As networks are proved to be untrustworthy by hackers and crackers, it has become mandatory to do such conversions while passing information through networks. These conversions are called Encryption methods and Decryption methods. Encryption is the process of converting the original message (also called as, plain text in scientific term) in to encrypted format (also called as, Cipher text in scientific term). Decryption is the reverse process of encryption where the encrypted message is converted to original format. Cryptography concentrates on four main issues. Those are,

1. Authentication

2. Confidentiality.

3. Integrity.

4. Non-repudiation.

There are many algorithms in cryptography. All these algorithms use three keys. They are Public key, Private Key and a Secret key. These keys are transferred from sender to receiver to provide confidentiality. If these keys are hacked, then the information becomes unsecured. Cryptography is widely used in banking procedures and other online applications of fund transfer, ATM machines, etc. and also transfers of files or documents or e-mails that contain secure data.

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