Abstract: Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (such as networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. With the migration of the data and the applications into the cloud, new security issues appear, with the fact that services are accessible anywhere any time lead to several potential risks. The most serious concerns are the possibility of lack of confidentiality and data security issues among the cloud users remain the principal inhibitor in adopting Cloud Computing Service. In this paper we have proposed new authentication system for cloud platform based on Multi level authentication having variable length onetime password (OTP) with mixture of numeric, alphanumeric and special character(s) for enhanced security in cloud authentication.

Keywords: Cryptography, Cloud Computing, OTP, RSA, AES.