A Secure and Privacy-Preserving Contact Tracing System for the Covid-19 Pandemic

由于新冠肺炎的无症状携带者数量众多，因此监测起来很复杂。确诊患者以及可能感染的个人都需要隔离，以控制病毒的传播。当一个人被确认感染时，卫生当局使用接触者追踪系统(CTS)来确定他们的下落，并获得一份与他们有过密切接触的人的名单，以便建议他们进行自我隔离。中国、韩国和新加坡等几个国家已经开发并使用了CTS。然而，这些CTS不保护用户的隐私：卫生当局跟踪每个人的下落，并可以识别确诊病例及其“密切”接触者。这种做法在欧洲和北美是不可接受的。因此，CTS提出了几项改善隐私的建议。鉴于最近发生的侵犯隐私丑闻，专有的封闭源代码解决方案(例如，来自Apple/Google)是不可接受的。一些建议的CTS存在固有的安全漏洞。其他人(例如，来自英国NHSX和蒙特利尔Mila实验室的)需要人工干预。在这个项目中，我们建议开发一个隐私保护的检疫通知系统。通过使用支持蓝牙和WiFi的移动设备，如果用户在该患者的实验室确认日期之前或之后14天遇到了确诊的新冠肺炎患者，该用户将能够收到隔离通知。未来的版本也将支持物联网传感器。我们的系统是我们所知的唯一满足以下要求的系统：1)安全(即，对网络攻击具有弹性)；2)完全自动化(即，除易于安装外，不依赖人工干预)；3)隐私保护(即，防止非法身份识别)；4)高效(即，隔离通知必须及时)。我们的系统在安全和隐私方面的保证将有利于它被加拿大人广泛采用，这反过来将确保我们阻止病毒的传播，并成功地重启我们的经济。

Due to a large number of asymptomatic carriers, the COVID-19 contagion is complex to monitor. Confirmed patients, as well as potentially infected individuals, are required to quarantine in order to control the spread of the virus. When a person is confirmed infected, a Contact Tracing System (CTS) is used by health authorities to determine their whereabouts and obtain a list of the individuals with 'close' encounters so that they can be advised to self-quarantine. Several countries such as China, South Korea and Singapore have developed and already use CTSs. However, these CTSs do not preserve the privacy of their user: health authorities keep track of everyone's whereabouts and can identify confirmed cases and their 'close' contacts. Such an approach is not acceptable in Europe and North America. Consequently, several CTS proposals have been put forth to improve privacy. Proprietary closed-source solutions (e.g., from Apple/Google) are not acceptable in light of recent breach-of-privacy scandals. Some proposed CTSs have inherent security vulnerabilities. Others (e.g., from UK's NHSX and from the MILA lab in Montreal) require human intervention. In this project, we propose developing a Privacy-Preserving Quarantine Notification System. Through the use of Bluetooth and WiFi-enabled mobile devices, a user will be able to receive a notification to quarantine if this user has encountered a confirmed Covid-19 patient 14 days before or after the lab confirmation date of this patient. A future version will also support IoT sensors. Our system is the only one we know that fulfills the following requirements: 1) secure (i.e., resilient to cyberattacks); 2) fully automated (i.e., not rely on human intervention except for its easy installation); 3) privacy preserving (i.e., prevent unlawful identification of an individual) and 4) efficient (i.e., quarantine notifications must be timely). The guarantees of our system with respect to security and privacy will favour its widespread adoption by Canadians, which, in turn, will ensure we stop the spread of the virus and successfully restart our economy.