A Dream Come True: Deletable Content in Immutable Storage

This work introduces DREAM, a novel construct that enables deletable content in otherwise immutable, decentralised storage systems such as Swarm. As an equitable and feasible response to the challenge of data destruction, DREAM reconciles the inherent persistence of content-addressed storage with the practical needs, user preferences, and legal requirements of permanent access revocation.

The paper contributes a new deletion model based on access revocation, and presents a mechanism that allows data-sharing users to grant—and later rescind—access to specific data for specific consumers. The solution leverages Swarm's distributed storage architecture to introduce a procedural way to retrieve decryption keys, realised by a network protocol.

The resulting system achieves the desired properties of deniability, revocability, expirability, addressability, and malleability without requiring trusted intermediaries or complex cryptographic primitives. The approach preserves the censorship resistance of decentralised systems allowing for sovereign control over data access by the original uploader, but not by any other party, thus avoiding any re-centralisation in order to achieve deletion. Security analysis shows that access revocation remains effective even under pervasive adversarial control.