The Block-based Mobile PDE Systems Are Not Secure -- Experimental Attacks

TL;DR

This paper experimentally demonstrates that block-layer mobile PDE systems are vulnerable to attacks that can compromise deniability by accessing raw NAND flash, highlighting security flaws in current implementations.

Contribution

The work provides the first experimental validation of deniability compromises in block-layer mobile PDE systems using a custom testbed and disk forensics.

Findings

Block-layer PDE systems can be compromised via raw NAND flash access.

Experimental validation confirms deniability breaches in practice.

Potential real-world attack issues are discussed.

Abstract

Nowadays, mobile devices have been used broadly to store and process sensitive data. To ensure confidentiality of the sensitive data, Full Disk Encryption (FDE) is often integrated in mainstream mobile operating systems like Android and iOS. FDE however cannot defend against coercive attacks in which the adversary can force the device owner to disclose the decryption key. To combat the coercive attacks, Plausibly Deniable Encryption (PDE) is leveraged to plausibly deny the very existence of sensitive data. However, most of the existing PDE systems for mobile devices are deployed at the block layer and suffer from deniability compromises. Having observed that none of existing works in the literature have experimentally demonstrated the aforementioned compromises, our work bridges this gap by experimentally confirming the deniability compromises of the block-layer mobile PDE systems. We have built a mobile device testbed, which consists of a host computing device and a flash storage device. Additionally, we have deployed both the hidden volume PDE and the steganographic file system at the block layer of the testbed and performed disk forensics to assess potential compromises on the raw NAND flash. Our experimental results confirm it is indeed possible for the adversary to compromise the block-layer PDE systems by accessing the raw NAND flash in practice. We also discuss potential issues when performing such attacks in real world.