A Privacy-Preserving Solution for Proximity Tracing Avoiding Identifier Exchanging

Abstract

Digital contact tracing is one of the actions useful, in combination with other measures, to manage an epidemic diffusion of an infectious disease in an after-lock-down phase. This is a very timely issue, due to the pandemic of COVID-19 we are unfortunately living. Apps for contact tracing aim to detect proximity of users and to evaluate the related risk in terms of possible contagious. Existing approaches leverage BLE or GPS, or their combination, even though the prevailing approach is BLE-based and relies on a decentralized model requiring the mutual exchange of ephemeral identifiers among users' smartphones. Unfortunately, a number of security and privacy concerns exist in this kind of solutions, mainly due to the exchange of identifiers, while GPS-based solutions (inherently centralized) may suffer from threats concerning massive surveillance. In this paper, we propose a solution leveraging GPS to detect proximity, and BLE only to improve accuracy, with no exchange of identifiers. Unlike related existing solutions, no complex cryptographic mechanism is adopted, while ensuring that the server does not learn anything about locations of users.

Delineating privacy aspects of COVID tracing applications embedded with proximity measurement technologies & digital technologies

“…Global Positioning System, or GPS, as one of the most widely adopted location data technologies, is also embedded in CTAs and has been critiqued for its potential risks to health surveillance, for recording users' exact locations, for threatening location privacy, and for exposing personal data [ 45 ]. While Bluetooth-enabled CTAs compromise privacy through the exchange of identifiers, GPS-enabled solutions violate privacy primarily through mass tracing [ 46 ].…”

Towards Defeating Mass Surveillance and SARS-CoV-2: The Pronto-C2 Fully Decentralized Automatic Contact Tracing System

“…Pinkas and Ronen [19], building upon a design similar to DP-3T, proposed a system with an improved resilience to relay attacks and a better verification of risks. Buccafurri et al proposed an alternative protocol that completely avoids the exchange of identifier over BLE and instead relies on GPS [7]. Public-key cryptography.…”

“…By using blind signatures based on RSA [6] with a length of 2048 bits for the modulus, the size of downloaded data is about 177MB 7 . The vast majority of daily downloaded data comes from the anonymous calls needed to evaluate the infection risk and their size is about 153MB, that can be processed as soon as received and deleted immediately after that, without flooding the memory of the smartphone.…”

An Advertising Overflow Attack Against Android Exposure Notification System Impacting COVID-19 Contact Tracing Applications

“…In [6], the author replayed released RPIs from the health authority and managed to trigger a exposure warning in the target. Others [18]- [20] defined scenarios such as advertising the received identifiers either immediately or at a later time. [22] presents an approach using a malicious Software Development Kit (SDK) injected in an App to replay received identifiers.…”

“…[21] mentions the Contact Pollution attack that works similarly to the Replay attack mentioned in [6]. Mitigation strategies for this type of attack have been proposed using protocols and location of devices [6], [17]- [20]. 2) Relay -This attack is similar to the Replay attacks; an attacker receives a RPI in one location and relays it to another device in a different location.…”