Design and implementation of a two-layered hybrid cryptosystem

A two-layered hybrid cryptosystem is proposed here. In symmetric key cryptosystem, the shared key is sent over a channel to the receiver. If an encrypted shared key is sent, the chance of intercepting the original key is reduced to some extent. So a hybrid cryptosystem is introduced here which is a combination of both asymmetric key and symmetric key cryptosystem. In the proposed technique, the encryption of the shared key is done using RSA algorithm by receiver's public key. Then the plain text is encrypted using the shared key to form the cipher text. The cipher text along with the encrypted shared key is sent to the receiver. The encrypted shared key is decrypted by the receiver using his or her private key. After that, using the decrypted key, the plain text is recovered by the receiver. Advantage of the proposed cryptosystem is that even if the shared key is intercepted during transmission, it is not the original shared key. The proposed technique can be implemented with files of any type.