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Deletion of content in large cloud storage systems

This thesis discusses the practical implications and challenges of providing secure deletion of data in cloud storage systems. Secure deletion is a desirable functionality to some users, but a requirement to others. The term secure deletion describes the practice of deleting data in such a way, that it can not be reconstructed later, even by forensic means. This work discuss the practice of secure deletion as well as existing methods that are used today. When moving from traditional on-site data storage to cloud services, these existing methods are not applicable anymore. For this reason, it presents the concept of cryptographic deletion and points out the challenge behind implementing it in a practical way. A discussion of related work in the areas of data encryption and cryptographic deletion shows that a research gap exists in applying cryptographic deletion in an efficient, practical way to cloud storage systems. The main contribution of this thesis, the Key-Cascade method, solves this issue by providing an efficient data structure for managing large numbers of encryption keys. Secure deletion is practiced today by individuals and organizations, who need to protect the confidentiality of data, after it has been deleted. It is mostly achieved by means of physical destruction or overwriting in local hard disks or large storage systems. However, these traditional methods of