Abstract: Thanks to the Internet, because of which the use of E-mails have become faster and easier. More and more companies are using it for better communication. However they are not aware about the risk they are going through .Obviously when you send a letter you know about the confidentiality but when it comes to E-mail system it involves a lots of information security risks. This paper proposes a theory on secure Emails. It develops a theory of CRYPTOGRAPHY In Cryptography ,encryption is a process by which message is encoded in such a way that only authorised user can access it .Encoded message is called Plain text and anonymously decoded message is called Cipher text and the process is called Decryption. For technical reasons, encryption scheme uses a pseudo random key, that is generated by an algorithm .This paper makes use of an algorithm called RSA algorithm for security related issues.
Keywords: RSA, Cryptography, Encryption, Decryption, Information Security.