BLUFFS: Bluetooth Forward and Future Secrecy Attacks and Defenses

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Presented at 37C3 2023 by

Ciao! We present the BLUFFS attacks (CVE-2023-24023), six novel attacks breaking Bluetooth's forward and future secrecy. Our attacks enable device impersonation and machine-in-the-middle across sessions by compromising and re-using one session key. We discuss the four vulnerabilities in the Bluetooth specification enabling the attacks, two of which are new and related to unilateral and repeatable session key derivation. We describe the toolkit we developed and open-sourced to test our attacks via firmware binary patching, our experiments where we exploited 18 heterogeneous Bluetooth devices, and the practical and backward-compliant session key derivation protocol we built to fix the attacks by design. We also cover related work like KNOB, BIAS, and BLUR, and educational Bluetooth security tips and tricks.