Alessandro Melloni defends his thesis

The defence will take place in the Nash auditorium at Vilvite (Thormøhlens Gate 51, 5006 Bergen). 

Main research findings

In his thesis, Alessandro Melloni presents "Counter Galois Onion" (CGO), a completely new form of encryption tailored for the Tor network. This work was carried out in a fruitful collaboration with co-authors Jean Paul Degabriele, Jean-Pierre Münch, and Martijn Stam. This solution makes it significantly harder for attackers to monitor data traffic and identify users. In collaboration with his co-authors, he has also developed a new and accurate framework for measuring and evaluating how much anonymity such networks actually provide under changing conditions. The right to online privacy is under pressure, and many people use Tor daily to communicate anonymously and bypass censorship.

Despite the network generally providing good protection, it has had an inherent weakness related to so-called "tagging attacks". Such attacks exploit the malleability of current encryption and allow an adversary to manipulate data traffic to reveal who is communicating with whom. The research solves this problem. The new CGO encryption builds on existing principles for authenticated encryption. It is fast, forward-secure, and effectively prevents attackers from modifying data traffic without it being immediately detected. The work is of great practical importance and provides a robust alternative to the current vulnerable system. The research has already been recognised by the Tor community, and the encryption method is now being integrated into "Arti", the next-generation version of the Tor network. In the long term, this will contribute to a safer, more anonymous digital everyday life for users worldwide.

Evaluation committee

• 1st Opponent: Associate Professor Håkon Jacobsen, Universitet i Oslo/Thales
• 2nd Opponent: Professor Stefanie Roos, University of Kaiserslautern-Landau
• Chair of the committee: Chief Research Scientist Håvard Raddum, Simula UiB

Leader of the public defence: Professor Chunlei Li, UiB

Supervisors

• Head of the Cryptography department and Chief Research Scientist Martijn Stam, Simula UiB (Main Supervisor)
• Professor Øyvind Ytrehus, UiB (co-supervisor)

Read more about the research in Norwegian in the original announcement at uib.no.