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

新型冠状病毒肺炎无症状感染者数量众多，监测难度较大。确诊患者和潜在感染者都需要隔离，以控制病毒的传播。当一个人被确诊感染时，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“密切接触”者的名单，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CTSs。然而，这些CTSs并没有保护其用户的隐私：卫生当局跟踪每个人的行踪，并可以确定确诊病例及其“密切”接触者。这种做法在欧洲和北美是不可接受的。因此，已经提出了几个CTS建议来改善隐私。鉴于最近的隐私泄露丑闻，专有的闭源解决方案（例如，来自Apple/ b谷歌）是不可接受的。一些建议的CTSs存在固有的安全漏洞。其他（例如，来自英国的NHSX和来自蒙特利尔的MILA实验室）需要人工干预。在这个项目中，我们建议开发一个保护隐私的检疫通知系统。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Covid-19患者，则可以收到隔离通知。未来的版本还将支持物联网传感器。我们的系统是我们所知道的唯一一个满足以下要求的系统：1)安全（即对网络攻击具有弹性）；2)全自动化（即除了安装方便外，不依赖于人为干预）；3)保护隐私（即防止非法识别个人）和4)高效（即检疫通知必须及时）。我们对安全和隐私的保障将有利于加拿大人广泛采用这一制度，这反过来将确保我们阻止病毒的传播并成功地重新启动我们的经济。

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.