Certificate Authorities (CAs) bootstrap HTTPS-based privacy and trust on the Internet by authenticating the identity of domain names via a process known as domain control validation (DV). Ironically, currently used DV mechanisms rely on unauthenticated web protocols, including plaintext DNS and HTTP, and have been shown vulnerable to a range of network attacks. To address this critical challenge, we propose a framework for cryptographic verification of domain control, which fundamentally mitigates network-layer attacks. Our framework rethinks live DV protocol mechanisms using a domain owner specified security policy which constrains CAs to use authenticated channels and provide cryptographic verification. Our approach minimizes deployment burden on CAs by leveraging existing pieces of the Web PKI and DNS ecosystems,such as Certificate Authority Authorization (CAA) policies and secure DNS. We demonstrate the security properties of our design formally using the Tamarin verification tool and empirically via ethically-conducted real-world attacks. We showcase the feasibility of our framework through collaboration with a major anonymous CA: we analyze DNS and certificate issuance practices of over 400M live domains to understand the current state of CAA policies and secure DNS. We also report on the CA’s experiences implementing parts of our design in production. Finally, to realize our framework in the live Web PKI, we led a successful standardization effort for mandatory use of secure DNS by CAs at the CA/Browser Forum.

Multiple Perspective Issuance Corroboration (MPIC) is a defense that strengthens the Domain Control Validation protocol run by Certificate Authorities (CAs) against network attacks (e.g., routing hijacks). Despite its recent adoption as a requirement by the CA/Browser Forum, the quantitative security benefits of MPIC in light of real-world routing behaviors are not well understood. We seek to address this challenge by creating a framework to test the effects of real-world BGP hijacks on millions of potential MPIC perspective deployments. Our framework launches around 1500 ethical BGP hijacks on IP prefixes we own and analyzes how potential MPIC perspectives route under these attacks. We consider over 100 global MPIC perspective locations spread across 3 major cloud providers. We find that optimal MPIC deployments can prevent certificate misissuance for over 87% of our evaluated real-world BGP hijacks. We further show that different routing behaviors by cloud providers, such as cold potato routing, have a substantial effect on MPIC's ability to limit the impact of BGP attacks. Finally, our framework computes optimized sets of MPIC perspective locations for CAs to use given their preference of cloud provider and perspective count. Our recommendations have already impacted the MPIC deployment at Google Trust Services, and have been adopted as the default recommendation by the Open MPIC project.

The SCION Next-Generation Network (NGN) architecture has expanded steadily since 2017, with today 20+ ISPs offering SCION connectivity. In production, IP-to-SCION-to-IP translation by SCION-IP-Gateways (SIGs) is used, such that applications are unaware of the NGN communication. To accelerate innovation and deployments, our aim is to increase the number of native SCION use cases, where the application is fully SCION-aware and optimizes communication across all path choices offered by the network. We set out to achieve two core objectives: (1) facilitating simple native connectivity for applications, and (2) enhancing the scalability of SCION deployment at academic sites.

Path aware networking (PAN) is a promising approach that enables endpoints to participate in end-to-end path selection. PAN unlocks numerous benefits, such as fast failover after link failures, application-based path selection and optimization, and native interdomain multi-path. The utility of PAN hinges on the availability of a large number of high-quality path options. In an inter-domain context, two core questions arise. Can we deploy such an architecture natively in today's Internet infrastructure without creating an overlay relying on BGP? Can we build a scalable multi-path routing system that provides a large number of high-quality paths?

In a world with increasing simplicity to store, transfer, and analyze large volumes of data, it becomes more and more important that data confidentiality and integrity be preserved in transit by default. Unfortunately, a large security gap exists between unprotected or low-security communication, such as opportunistic encryption and trust-on-first-use (TOFU) security, and high-security communication, such as TLS using server certificates or DNSSEC. Our goal is to reduce this gap and achieve a base layer for authentication and secrecy that is strictly better than TOFU security. We achieve this by designing PILA, a novel authentication method with dynamic trust anchors, which leverages irrefutable cryptographic proof of misbehavior to incentivize benign behavior. We implement PILA extensions for SSH, TLS, and DNS and show that the overhead for a typical SSH and TLS connection establishment is negligible, and that PILA only causes a marginal processing overhead of $\sim 100\ \mu \mathrm{s}$ per DNS response at the endpoints.