eng Science and Education Publishing American Journal of Information Systems 2374-1988 2016-03-16 4 2 17 31 10.12691/ajis-4-2-1 AJIS2016421 article Shyam Nandan Kumar shyamnandan.mec@gmail.com 1 Amit Vajpayee 2 M.Tech-Computer Science and Engineering, Lakshmi Narain College of Technology-Indore (RGPV, Bhopal), MP, India Department of Computer Science and Engineering, Lakshmi Narain College of Technology-Indore (RGPV, Bhopal), MP, India Security concern has become the biggest obstacle to adoption of cloud because all information and data are completely under the control of cloud service providers. To provide optimal services on cloud, this paper introduces a new distributed and scalable data sharing scheme for data owners in clouds that supports anonymous authentication. Proposed ASP (Advanced Security Protocol) protocol is a cryptographic access control protocol based on key-updating scheme referred to as Advanced Key Update (AKU). The main advantage of the AKU scheme its support for efficient delegation and revocation of privileges in hierarchies without requiring complex cryptographic data structures. Proposed ASP protocol also includes a new digital signature scheme that enables cloud providers to ensure that requests are submitted by authorized end-users, without learning their identities. User Revocation facility is also supported by proposed ASP. In this paper various existing approaches and issues related to data encryption and message authentications are also discussed. At last, experiment results are analyzed and performances are evaluated. The main aim of the paper is to provide more visibility and control to the end-users and close the gap between capabilities of existing solutions and new requirements of cloud-based systems. http://pubs.sciepub.com/ajis/4/2/1/ajis-4-2-1.pdf cloud computing data sharing decryption encryption concurrent access distributed system web message signing and verification data confidentiality message authentication cloud security