Leakage-resilient Cryptography with key derived from sensitive data
This addresses storage efficiency for users in leakage-resilient cryptography, though it is incremental as it builds on existing protocols.
The paper tackles the problem of large secret key storage in the Bounded Retrieval Model by proposing a method to derive keys on-the-fly from weakly random private data, eliminating extra storage while maintaining similar security levels and ensuring data privacy.
In this paper we address the problem of large space consumption for protocols in the Bounded Retrieval Model (BRM), which require users to store large secret keys subject to adversarial leakage. We propose a method to derive keys for such protocols on-the-fly from weakly random private data (like text documents or photos, users keep on their disks anyway for non-cryptographic purposes) in such a way that no extra storage is needed. We prove that any leakage-resilient protocol (belonging to a certain, arguably quite broad class) when run with a key obtained this way retains a similar level of security as the original protocol had. Additionally, we guarantee privacy of the data the actual keys are derived from. That is, an adversary can hardly gain any knowledge about the private data except that he could otherwise obtain via leakage. Our reduction works in the Random Oracle model.