ADEC: Assured Deletion and Verifiable Version Control for Cloud Storage

Although cloud storage offers a number of attractive features, it also raises various security concerns. In particular, cloud storage of sensitive information, such as medical or trade records, requires measures to be taken not only for privacy protection, but also for assured deletion and verifiable version control. Even though there are methods for realizing both assured deletion and version control in cloud storage, they cannot guarantee the integrity of files and their versioning order. Therefore, we propose a system referred to as ``Assured Deletion and verifiable version Control (ADEC)´´, which is implemented as a virtual file system capable of taking snapshots in cloud storage. The main ideas behind ADEC are a scheme for generating chained keys and a scheme for verifiable version control with hysteresis signatures. This method can be used not only for protection of privacy, but also for assured deletion of specific versions and all older versions in a single operation. In addition, the integrity of each file version can be verified with the hysteresis signature scheme, which makes it impossible to implement rollback and reordering attacks.