Digitally signed certificates issued by trusted certificate authorities (CAs) protect users from man-in-the-middle attacks by vouching for the domain names of websites. However, the process CAs use to issue certificates is vulnerable to network-level attacks that can allow an adversary to obtain a certificate of a domain it does not control. These mis-issued certificates can allow an adversary to impersonate crucial websites (such as banks) and intercept (or modify) sensitive internet traffic. Our research focuses on understanding and preventing Border Gateway Protocol (BGP) attacks that could let an adversary obtain a mis-issued certificate. The primary aspects of our research are:

  • Modeling BGP attacks to determine the extent of the vulnerability
  • Launching ethical real-world attacks and measuring the responses of leading CAs
  • Developing defenses to these attacks

Download our USENIX paper

Get more information about our USENIX Security paper here.
Read our talk and view our live attack demonstration here.


This project recieved coverage on freedom to tinker.


The following team of researchers at Princeton University contributed to this project:

Partnership With Let's Encrypt Logo

Thanks to support from the Open Technology Fund we have been able to partner with the Let's Encrypt CA to help us secure the internet against these attacks. Let's Encrypt has a preliminary implementation of our suggested countermeasures deployed to their testing environment, and is sharing their data with us to help us better understand the attack surface and develop countermeasures.