Abstract:  This paper presents a “contract”-related certification protocol in a cloud computing
alliance environment. With a signature algorithm of combined public and private
data, “contract” trust relationship is built among alliance clouds. By taking advantage of
the trust relationship, distributed management of user identity information and “contract”
related certification are realized in the cloud alliance. The proposed protocol uses bulletin
board, time stamp, signature, and anti-collision hash function to reduce information interaction,
effectively preventing data tampering, replay, and middle attack. Theoretical
analysis shows that the proposed protocol is secure and efficient. It requires less computation
and communication overhead, and provides a concise and security solution for alliance
identity authentication in a cloud environment.

Key words: cloud computing alliance, “contract”-related certification, signature algorithm, protocol