Any communication in the language that you and I speak-that is the human language, takes the form of plain text or clear text. That is, a message in plain text can be understood by anybody knowing the language as long as the message is not codified in any manner. So, now we have to use coding scheme to ensure that information is hidden from anyone for whom it is not intended, even those who can see the coded data. Cryptography is the art of achieving security by encoding messages to make them

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... nreadable. Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering. Cryptography is used in applications present in technologically advanced societies; examples include the security of ATM cards, computer passwords and electronic commerce, which all depend on cryptography. There are two basic types of cryptography: Symmetric Key and Asymmetric Key. Symmetric key algorithms are the quickest and most commonly used type of encryption. Here, a single key is used for both encryption and decryption. There are few well-known symmetric key algorithms i.e. DES, RC2, RC4, IDEA etc. This paper describes cryptography, various symmetric key algorithms in detail and then proposes a new symmetric key algorithm. Algorithms for both encryption and decryption are provided here. The advantages of this new algorithm over the others are also explained.