# Enhancing the Privacy of Network Services through Trusted Computing
## 2 Backgrounds and Related Work  
### The Addressing and Discovering Service  
When an application requests a website or a networking service by a domain name, the application first sends a query request to the recursive resolver. If the resolver caches the appropriate IP address, it will forward the address directly to the application. Otherwise, the resolver queries other name servers (NS) such as root name servers, top-level domain name servers (TLD), and authoritative name servers, as well as hierarchical trees. The iterative queries continue until it retrieves a DNS record containing the requested IP address, which will be forwarded back to the requester in turn. The application can request the actual webpage once the DNS lookup returns the IP address for a queried domain name. The security of the DNS infrastructure is one of the core requirements for Internet services. To address the drawbacks of DNS, many improvements and extensions follow [12; 14]. DNS evolved from a simple name-IP conversion service to a complex and secure resolution service. Table 1 presents the feature comparison of existing methods. The plain DNS denotes the normal DNS protocol. If the performance of the new mechanism is on the same order of magnitude as plain DNS when handling DNS requests, we think it has performance advantages. Deployability denotes deployment friendliness; that is, whether this method needs to update or migrate the existing DNS software. If the proposed DNS scheme is compatible with the existing technologies, such as TLS and HTTPS, we think it is easy to deploy. If one scheme can provide integrity and origin authentication for DNS data, we consider it to have authentication features. The security of the DNSinfrastructure is one of the core requirements for Internet services. The breach in DNS security and privacy will affect the trust-worthiness of the Internet in turn. The DNSSEC scheme [8] is first proposed to complement the original protocol for DNS data integrity and origin authentication. The Internet Engineering Task Force (IETF) further proposes DNS-over-HTTPS (DoH) and DNS-over-TLS (DoT) to standardize DNS encryption and protect DNS from eavesdropping and manipulation of DNS data. With increasing focus on privacy and iterative updating of the software and system, DNS clients supporting DoT and DoH are increasing. However, two significant drawbacks remain. The only score DoTT did not achieve against the plain DNS was performance, which is an essential cost of securing a system. On the other hand, the prototype system we implemented only utilizes SGX features without further optimization. We will discuss more details about DoTT in Section 3. The first is software vulnerabilities. As mass devices need cross-domain communication, the Internet needs perfect resource addressing technology to ensure that the related information can be efficiently addressed, located, and queried. In the original design and still dominant use of DNS, queries are sent in plaintext. The metadata in a DNS query contains sensitive information, including accessed hostname, websites, as well as IP addresses identifying personal devices. This means that anyone on the network path between personal devices and DNS resolvers can see the query. The breach in DNS security and privacy will affect the trust-worthiness of the Internet in turn. The resource records are not signed and anti-counterfeiting protected. Therefore, the DNS protocol is vulnerable to caching and malicious attacks such as poisoning, eavesdropping, tampering, etc. Further, it may reveal significant information about users and result in a serious threat to individual privacy [13]. The resolver can still associate all queries with the customer's sensitive data. There is a great challenge to ensure the integrity of DNS programs and the reliability of responses. The second is backward compatibility. A large spectrum of improved systems and architectures for DNS have been proposed without considering the compatibility with existing systems.