Ovid: Message-based Automatic Contact Tracing

Abstract

The COVID-19 pandemic created various new challenges for our societies. Quickly discovering new infections using automated contact tracing without endangering privacy of the general public is one of these. Most discussions concerning architectures for contact tracing applications revolved around centralized against decentralized approaches. In contrast, the system proposed in this work builds on the idea of messagebased contact tracing to inform users about their risk. Our main contribution is the combination of a blind-signature approach to verify infections with an anonymous postbox service. In our evaluation, we analyze all components in our system for performance and privacy, as well as security. We also derive parameters for operating our system in a pandemic scenario.

Digital Contact Tracing Solutions: Promises, Pitfalls and Challenges

“…Advanced Privacy Techniques. There are several (mainly cryptography-based) privacy techniques that have been considered to enhance privacy of DCT, e.g., Blind signatures [28], [25], Blockchain [25], Private Set Intersection (PSI)/filter [27], and secret sharing [19]. Unfortunately, none of these contact tracing approaches have been used in practice yet.…”

“…However, this threat can be effectively mitigated by applying appropriate anonymization techniques like blind signatures with an anonymous postbox service [28] to the upload process of encounter tokens. This assures that even a malicious service provider A 𝑠 cannot link individual encounter tokens of infected users, thereby limiting the trackability of individual system users to relatively short time frames of, e.g., 15 minutes.…”

“…Blind Signature. Some approaches, e.g., [28], [25] propose using a blind signature scheme to verify the authenticity of encounter information, e.g., the temporary keys that infected users upload to the tracing service provider SP. In contrast to common approaches in which HA gives a unique transaction number (TAN) to each of the infected users for uploading their data, allowing HA to link infected users in a DCT to HA's patient data, blind signature-based approaches prevent this by enabling HA to "blindly" sign the temporary keys of infected users without knowing the actual content.…”

Amostragem gaussiana eficiente para a construção de sistemas criptográficos pós-quânticos baseados em reticulados.

“…Additionally,(WANG; LYU; LIU, 2019) presents the DGS topic from an information theory perspective, and (CHEN, 2019) approaches the decision versions of RLWE with possible DGS primitives, questioning the hardness for some cyclotomic number fields and specific DGS interval widths. Further insights on DGS implementation, regarding generic and specific prerequisites, e.g., isochrony and CDT implications, are offered by (REPARAZ;BALASCH;VERBAUWHEDE, 2016;KARMAKAR et al, 2018;WALTER, 2018;WANG;, and also by two C language implementations, namely the GNU Scientific Library (GSL) (GALASSI; THEILER, 2019), and the Open Quantum Safe library (liboqs) (STEBILA; MOSCA,…”

“…Mitigation measures to timing and other sidechannel attacks can be implemented in application, operating system, and hardware levels. As an LWE-based proposal, this work addresses timing-attack risks through vulnerability-reduction measures in the application level, implementing isochrony in parts of its construction (ORTIZ, 2016;REPARAZ;BALASCH;VERBAUWHEDE, 2016).…”