Providing Cloud Storage Auditing Through Verifiable Key Update Outsourcing

Abstract

In many security applications, key-exposure resistance has long been a pressing concern for a comprehensive cyber defence strategy. How to address this critical exposure issue in the context of cloud storage auditing has been proposed and investigated as of late. Existing solutions to the problem necessitate that the client updates his secret keys at regular intervals, which can be a significant burden for clients with limited computational resources, like mobile phones. To provide maximum client transparency during key updates, we propose a novel paradigm in this paper: cloud storage auditing combined with the verifiable outsourcing of key updates. In this model, the client doesn't have to worry about keeping track of key updates because they can be safely delegated to a trusted third party. In particular, we adapt the role of the third-party auditor (TPA) from numerous existing public auditing designs, giving it responsibility for both the auditing of the storage and the security updates of keys in order to prevent key exposure. Our scheme requires TPA to keep only an encrypted copy of the client's secret key while performing these otherwise onerous tasks on the client's behalf. When transferring data to the cloud, the client only needs to get the encrypted secret key from the TPA. Further, our architecture provides the client with the means to confirm the authenticity of the TPA's supplied encrypted secret keys. The whole auditing process with key exposure resistance is made as clear to the client as possible by the inclusion of these prominent features. The definition and underlying security model of this paradigm are formally outlined. Our rigorously tested and simulated implementations of the detailed designs have proven to be safe and effective in practice.