Secure data deletion from persistent media

Secure deletion is the task of deleting data irrecoverably from a physical medium. In this work, we present a general approach to the design and analysis of secure deletion for persistent storage that relies on encryption and key wrapping. We define a key disclosure graph that models the adversarial knowledge of the history of key generation and wrapping. We introduce a generic update function and prove that it achieves secure deletion of data against a coercive attacker; instances of the update function implement the update behaviour of all arborescent data structures including B-Trees, extendible hash tables, linked lists, and others. We implement a B-Tree instance of our solution. Our implementation is at the block-device layer, allowing any block-based file system to be used on top of it. Using different workloads, we find that the storage and communication overhead required for storing and retrieving B-Tree nodes is small and that this therefore constitutes a viable solution for many applications requiring secure deletion from persistent media.