Assessing the Privacy Benefits of Domain Name Encryption

Abstract

As Internet users have become more savvy about the potential for their Internet communication to be observed, the use of network traffic encryption technologies (e.g., HTTPS/TLS) is on the rise. However, even when encryption is enabled, users leak information about the domains they visit via DNS queries and via the Server Name Indication (SNI) extension of TLS. Two recent proposals to ameliorate this issue are DNS over HTTPS/TLS (DoH/DoT) and Encrypted SNI (ESNI). In this paper we aim to assess the privacy benefits of these proposals by considering the relationship between hostnames and IP addresses, the latter of which are still exposed. We perform DNS queries from nine vantage points around the globe to characterize this relationship. We quantify the privacy gain offered by ESNI for different hosting and CDN providers using two different metrics, the k-anonymity degree due to co-hosting and the dynamics of IP address changes. We find that 20% of the domains studied will not gain any privacy benefit since they have a one-to-one mapping between their hostname and IP address. On the other hand, 30% will gain a significant privacy benefit with a k value greater than 100, since these domains are co-hosted with more than 100 other domains. Domains whose visitors' privacy will meaningfully improve are far less popular, while for popular domains the benefit is not significant. Analyzing the dynamics of IP addresses of long-lived domains, we find that only 7.7% of them change their hosting IP addresses on a daily basis. We conclude by discussing potential approaches for website owners and hosting/CDN providers for maximizing the privacy benefits of ESNI.

Development of an algorithm to protect user communication devices against data leaks

“…The DNS traffic leaks were evaluated in [17]. Papers [18][19][20] analyze the pros and cons of DNS traffic encryption using DNS over TLS (DoT) protocols, DNS over HTTPS (DoH). Study [18] found that even when encryption is enabled, users' data outflow through their DNS queries.…”

“…Papers [18][19][20] analyze the pros and cons of DNS traffic encryption using DNS over TLS (DoT) protocols, DNS over HTTPS (DoH). Study [18] found that even when encryption is enabled, users' data outflow through their DNS queries. In addition, it was found in [19] that doT and DoH protocols are supported by only a small number of DNS servers.…”

K-resolver: Towards Decentralizing Encrypted DNS Resolution

“…Our threat model is oblivious to the relationship between hosting providers and operators of the recursor, who may be the same entity. Nonetheless, we consider this relationship as an orthogonal problem due to the current state of web co-location, in which the vast majority of web servers are hosted by only a handful of hosting providers [42], among which Google and Cloudflare are dominant [14]. For example, with our K-resolver mechanism, the domain name of a website may be resolved by a recursor that does not belong to Google or Cloudflare.…”

“…The rapid development and deployment of DoH/DoT has attracted many researchers to study these new protocols. Recent studies mainly investigate two aspects of DoH/DoT: privacy [4,14,18,36] and performance [3,6,30].…”

“…In terms of user privacy, researchers aim to tackle two types of adversaries. The first type includes "nosy" on-path observers, who have the privilege to monitor the encrypted traffic between the user and the DoH/DoT server, trying to predict the website being visited by the user using different traffic fingerprinting techniques [4,14,18]. The second type of adversary is located at the recursor, such as compromised or malicious recursors that have illicit intentions to use of the user's online history [36].…”