Enhanced authentication for outsourced educational contents through provable block possession

In recent years, the volume of educational contents has been explosively increased thanks to the rapid development of multimedia technologies. Furthermore, the development of smart devices has made various educational institutes use them as effective learning tools. Since more and more educational contents become available not only at school zone but at a variety of online learning systems, it becomes increasingly unaffordable for a single educational contents provider to store and process them locally. Therefore, many educational contents providers are likely to outsource the contents to cloud storage for cost saving. These phenomena raise one serious concern: how to authenticate educational contents users in a secure and efficient way? The most widely used password-based authentication suffers from numerous drawbacks in terms of security. Multi-factor authentication protocols based on diverse communication channels such as SMS, biometric, hardware token could enhance security, however they inevitably bring poor usability. To this end, we present a data block-based authentication scheme, which provides provable security and guarantees usability invariant such that users do nothing but entering a password. In addition, the proposed scheme supports efficient user revocation. To the best of our knowledge, our scheme is the first data block-based authentication scheme for outsourced educational contents that is provably secure without usability degradation. The experiment on Amazon EC2 cloud shows that the proposed scheme guarantees nearly constant time for user authentication.