Collaborative cloud business models enable a new dimension of business by giving option to the third party software vendors to deploy their software in the cloud for offering software as a service (SaaS) to the users. However, the secure provisioning of resources requires scalable architecture with efficient authentication for configuring the collaborative software services in the cloud. In this paper, we propose a novel hierarchical certificateless aggregate signature to provide a scalable authentication model for SaaS in cloud computing. Our proposed scheme is secure under the adaptive chosen-message attack in the random oracle model with the hardness assumption of Computational Diffie–Hellman (CDH) problem and Decisional Diffie–Hellman (DDH) problem. Furthermore, our proposed scheme is highly efficient regarding low overhead on computation and communication cost.

协作式云业务模型通过允许第三方软件供应商选择在云中部署其软件以向用户提供软件即服务（SaaS），从而实现了新的业务领域。但是，资源的安全供应需要具有有效身份验证的可伸缩体系结构，以便在云中配置协作软件服务。在本文中，我们提出了一种新颖的分层无证书聚合签名，以为云计算中的SaaS提供可扩展的身份验证模型。我们提出的方案在随机预言模型的自适应选择消息攻击下具有计算Diffie-Hellman（CDH）问题和决策Diffie-Hellman（DDH）问题的硬度假设是安全的。此外，