Paper 2024/874

Fake It till You Make It: Enhancing Security of Bluetooth Secure Connections via Deferrable Authentication

Abstract

The Bluetooth protocol for wireless connection between devices comes with several security measures to protect confidentiality and integrity of data. At the heart of these security protocols lies the Secure Simple Pairing, wherewith the devices can negotiate a shared key before communicating sensitive data. Despite the good intentions, the Bluetooth security protocol has repeatedly been shown to be vulnerable, especially with regard to active attacks on the Secure Simple Pairing. We propose here a mechanism to limit active attacks on the Secure Connections protocol (the more secure version of the Secure Simple Pairing protocol), without infringing on the current Bluetooth protocol stack specification. The idea is to run an authentication protocol, like a classical challenge-response step for certified keys, within the existing infrastructure, even at a later, more convenient point in time. We prove that not only does this authentication step ensure freshness of future encryption keys, but an interesting feature is that it—a posteriori—also guarantees security of previously derived encryption keys. We next argue that this approach indeed prevents a large set of known attacks on the Bluetooth protocol.