International Association
for Cryptologic Research

Sensitive pictures such as passport photos and nudes are commonly shared through mobile chat applications. One popular strategy for the privacy protection of this material is to use ephemeral messaging features, such as the view once snaps in Snapchat. However, design limitations and implementation bugs in messaging apps may allow attackers to bypass the restrictions imposed by those features on the received material. One way by which attackers may accomplish so is by tampering with the software stack on their own devices. In this paper, we propose and test a protection strategy based on a multiplatform system that encrypts and decrypts sensitive pictures on top of messaging apps and performs remote attestation with available app integrity APIs to safeguard its security. Our analysis and experiments show that, compared to previous proposals for image encryption in a middleware, remote attestation offers increased security, adds privacy benefits, simplifies integration, and improves usability by not requiring users to exchange key material a priori. In our experiments, it incurs an added average latency of 3.8 and 4.5 seconds when sending and receiving private pictures, respectively.