Abstract: Cloud computing, is a technology that provides dynamic and scalable resources for computing as pay per use through internet. In cloud identifying an appropriate user is a challenging task for the service provider, but basing on the unique identification methods like password, smartcard and many other different authentication techniques, a user can be identified. Even though many authentication schemes are introduced in past but they failed with various drawbacks. This paper is to introduce an authentication scheme using Modified Double ceasar cipher encryption technique in which the password is encrypted using a key that is kept secret and is tough to guess. Our encryption technique is secured from the attacks like guessing or brute force attack. The proposed system uses a Modified Double ceasar cipher encryption technique which uses the English alphabets to create password and a key to encrypt basing on the value of its character by performing addition a cipher key is generated and stored in the waveform. The proposed scheme has an interesting feature of storing and representing the password in waveforms using Manchester encoding [7], which makes the system more effective in avoiding some attacks like guessing attack and tampering the password. The work clearly specifies the different authentication schemes used so far.

Keywords: Double ceasar cipher, Encryption, Decryption, Authentication, waveform.