PACT: Privacy Sensitive Protocols and Mechanisms for Mobile Contact Tracing (2004.03544v4)

Abstract: The global health threat from COVID-19 has been controlled in a number of instances by large-scale testing and contact tracing efforts. We created this document to suggest three functionalities on how we might best harness computing technologies to supporting the goals of public health organizations in minimizing morbidity and mortality associated with the spread of COVID-19, while protecting the civil liberties of individuals. In particular, this work advocates for a third-party free approach to assisted mobile contact tracing, because such an approach mitigates the security and privacy risks of requiring a trusted third party. We also explicitly consider the inferential risks involved in any contract tracing system, where any alert to a user could itself give rise to de-anonymizing information. More generally, we hope to participate in bringing together colleagues in industry, academia, and civil society to discuss and converge on ideas around a critical issue rising with attempts to mitigate the COVID-19 pandemic.

• The paper proposes PACT, a set of privacy-sensitive protocols and mechanisms for mobile contact tracing that avoids reliance on third parties.
• PACT incorporates mobile-assisted interviews, narrowcasting, and privacy-centric tracing using proximity signals like Bluetooth and sophisticated cryptographic protocols.
• This research lays a foundation for balancing privacy and public health needs in digital interventions, highlighting the challenge of adoption and the system's supplementary role.

An Analysis of "PACT: Privacy-Sensitive Protocols And Mechanisms for Mobile Contact Tracing"

The paper under analysis, titled "PACT: Privacy-Sensitive Protocols And Mechanisms for Mobile Contact Tracing," presents a detailed exploration of protocols aimed at balancing the effectiveness of digital contact tracing for infectious diseases like COVID-19 with the preservation of individual privacy and civil liberties. This exploration is particularly critical in the context of the global health crisis precipitated by COVID-19, where contact tracing emerged as a key public health intervention to limit the spread of the virus.

Core Contributions

The paper's main contributions can be compartmentalized into proposing a third-party-free protocol for mobile contact tracing and emphasizing privacy and security in such systems. The approach posits that avoiding reliance on central authorities or third parties for data management can alleviate potential privacy invasions and misuse. The authors introduce the "PACT" approach, which involves a combination of functionalities: mobile-assisted contact tracing interviews, narrowcasting of public health messages, and privacy-centric mobile tracing.

1. Mobile-Assisted Interviews - This functionality enables users to voluntarily augment contact interviews with information stored on their devices, enhancing recall accuracy and reducing burden on public health authorities, while ensuring that data remains private unless consciously shared.
2. Narrowcast Messages - Public health authorities can issue geographically and temporally targeted alerts. Such messages could, for example, inform citizens about exposure risks in specific locations without revealing who was exposed, leveraging the user's device to assess relevance and consent to receive alerts.
3. Privacy-Sensitive Mobile Tracing - The paper provides innovative solutions to leverage proximity-based signals, such as Bluetooth, to determine potential exposures without revealing absolute locations. It presents technical protocols that rigorously protect user identities, allowing users to remain effectively anonymous unless they choose to disclose their information due to a positive infection status.

Privacy and Security Considerations

The authors tackle the challenging task of maintaining privacy while ensuring effective tracing. The proposed methods provide sophisticated cryptographic protocols, notably employing pseudorandom number generation and secure cryptographic signatures to enforce privacy and prevent misuse. The paper effectively addresses common civilian concerns, such as potential re-identification risks, replay attacks, and the need for integrity in reporting systems. For instance, the protocol ensures that data symmetrically remains on individuals' devices, with exposure notifications determined locally rather than sent to centralized servers, minimizing data leaks.

Broader Implications and Challenges

The implications of the research are significant for public health informatics and digital privacy governance. The proposed methodologies present a foundation for future mobile health applications where the intersection of privacy and efficiency is pivotal. However, achieving high adoption rates, which are crucial for the system’s effectiveness, remains a challenge. The paper notes that conventional contact tracing cannot be supplanted entirely given technology access disparities, emphasizing the role of such digital systems as supplementary to traditional methods.

Speculation on Future Developments

Looking forward, this research suggests potential developments in decentralized identity management and federated learning frameworks that further mitigate privacy risks. Integration with broader epidemiological surveillance systems, which do not undermine civil liberties, stands as a possible pathway for advancing public health strategies. Moreover, the deployment of such systems will likely spur discussions and development of robust policy frameworks that oversee privacy standards and ethical guidelines.

In conclusion, this paper lays a critical foundation for privacy-sensitive contact tracing technologies that balance individual rights with public health needs. Its detailed exploration of cryptographic protocols and real-world implications provides a comprehensive guide for future work in this domain. As digital health interventions become more prevalent, findings from this research will prove pivotal in shaping privacy-respecting policies and technical frameworks.