Understanding the Impact of Encrypted DNS on Internet Censorship Lin Jin Shuai Hao Haining Wang Chase Cotton University of Delaware Old Dominion University Virginia Tech University of Delaware Newark, Delaware, USA Norfolk, Virginia, USA Arlington, Virginia, USA Newark, Delaware, USA
[email protected] [email protected] [email protected] [email protected] ABSTRACT 1 INTRODUCTION DNS traffic is transmitted in plaintext, resulting in privacy leakage. The Domain Name System (DNS) provides important mappings To combat this problem, secure protocols have been used to encrypt between domain names and their numerical IP addresses to direct DNS messages. Existing studies have investigated the performance users to Internet services. As a fundamental component of the overhead and privacy benefits of encrypted DNS communications, Internet, DNS was designed as an unencrypted protocol. However, yet little has been done from the perspective of censorship. In this this allows eavesdroppers to sniff the domain that a user is going paper, we study the impact of the encrypted DNS on Internet cen- to visit, raising a privacy concern. In order to mitigate this privacy sorship in two aspects. On one hand, we explore the severity of DNS issue, secure protocols, such as DNS-over-TLS (DoT) [29] and DNS- manipulation, which could be leveraged for Internet censorship, over-HTTPS (DoH) [25], have been proposed to encrypt DNS traffic, given the use of encrypted DNS resolvers. In particular, we perform and DNS service providers, such as Google and Cloudflare, have 7.4 million DNS lookup measurements on 3,813 DoT and 75 DoH gradually supported these protocols on their resolvers.