I2P: Study of the Network and its Censorship Resistance

grarpamp grarpamp at gmail.com
Fri Jan 25 22:36:29 PST 2019


 Tor and I2P are well-known anonymity networks used by many
individuals to protect their online privacy and anonymity. 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. In contrast, I2P does not rely on
centralized directory servers, and thus obtaining a complete view of
the network is challenging. 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. We find that there are currently around 32K active I2P
peers in the network on a daily basis. Of these peers, 14K are located
behind NAT or firewalls.
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. 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. 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. Finally,
we discuss the security consequences of the network being blocked, and
directions for potential approaches to make I2P more resistant to

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