Paper 2024/1782

Is Periodic Pseudo-randomization Sufficient for Beacon Privacy?

Liron David, Weizmann Institute of Science and Google Research
Avinatan Hassidim, Bar-Ilan University and Google Research
Yossi Matias, Tel-Aviv University and Google Research
Moti Yung, Columbia University and Google Privacy, Security, and Safety Research
Abstract

In this paper, we investigate whether the privacy mechanism of periodically changing the pseudorandom identities of Bluetooth Low Energy (BLE) beacons is sufficient to ensure privacy. We consider a new natural privacy notion for BLE broadcasting beacons which we call ``Timed-sequence- indistinguishability'' of beacons. This new privacy definition is stronger than the well-known indistinguishability, since it considers not just the advertisements' content, but also the advertisements' broadcasting times which are observable in the physical world. We then prove that beacons with periodically changing pseudorandom identities do not achieve timed-sequence- indistinguishability. We do this by presenting a novel privacy attack against BLE beacons, which we call the ``Timer Manipulation Attack.'' This new time-based privacy attack can be executed by merely inserting or reinserting the beacon's battery at the adversary's chosen time. We performed this attack against an actually deployed beacon. To mitigate the ``Timer Manipulation Attack'' and other attacks associated with periodic signaling, we propose a new countermeasure involving quasi-periodic randomized scheduling of identity changes. We prove that our countermeasure ensures timed-sequence indistinguishability for beacons, thereby enhancing the beacon's privacy. Additionally, we show how to integrate this countermeasure in the attacked system while essentially preserving its feasibility and utility, which is crucial for practical industrial adoption.

Metadata
Available format(s)
PDF
Category
Attacks and cryptanalysis
Publication info
Published elsewhere. 25th Privacy Enhancing Technologies Symposium (PETS 2025)
Keywords
PrivacyIoTbroadcasting beaconsBLEEphemeral IDstime-based attackscountermeasuresrandomized scheduling
Contact author(s)
lirondavid @ gmail com
avinatan @ google com
yossi @ google com
motiyung @ gmail com
History
2024-11-04: last of 3 revisions
2024-11-01: received
See all versions
Short URL
https://ia.cr/2024/1782
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2024/1782,
      author = {Liron David and Avinatan Hassidim and Yossi Matias and Moti Yung},
      title = {Is Periodic Pseudo-randomization Sufficient for Beacon Privacy?},
      howpublished = {Cryptology {ePrint} Archive, Paper 2024/1782},
      year = {2024},
      url = {https://eprint.iacr.org/2024/1782}
}
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