In this dissertation, we present two related lines of research that seek to tackle the twin problems of Internet censorship and online surveillance via an empirical lens. Internet censorship and online surveillance have led to severe human rights violations, including the freedom of expression, the right to information, and privacy. Malicious actors around the world, ranging from nation states to private organizations, are increasingly making use of technologies to not only control the free flow of information, but also eavesdrop on Internet users' online activities. With the Internet having become an indispensable means of communication in modern society, censorship and surveillance in cyberspace are getting more prevalent.

Finally, we discuss the security consequences of the network being blocked, and directions for potential approaches to make I2P more resistant to blocking. This amounts to severe network impairment: a blocking rate of more than 70% is enough to cause significant latency in web browsing activities, while blocking more than 90% of peer IP addresses can make the network unusable. Despite the decentralized characteristics of I2P, we discover that a censor can block more than 95% of peer IP addresses known by a stable I2P client by operating only 10 routers in the network. Using the collected network data, we examine the blocking resistance of I2P against a censor that wants to prevent access to I2P using address-based blocking techniques. Of these peers, 14K are located behind NAT or firewalls. We find that there are currently around 32K active I2P peers in the network on a daily basis.

In this work, we conduct an empirical study of the I2P network, in which we measure properties including population, churn rate, router type, and the geographic distribution of I2P peers. In contrast, I2P does not rely on centralized directory servers, and thus obtaining a complete view of the network is challenging. Tor's centralized directory services facilitate the understanding of the Tor network, as well as the measurement and visualization of its structure through the Tor Metrics project. Tor and I2P are well-known anonymity networks used by many individuals to protect their online privacy and anonymity.

Tor bridge nodes