Helger Lipmaa

Research Background

I have been an active cryptography researcher since around 1997. My first research topic was time-stamping --- combined with authenticated data structures and accumulators. I have researched many cryptographic topics, starting from differential cryptanalysis and ending with MPC. However, since 2001 I have been active in zero-knowledge research. I wrote my first SNARK paper in 2008, where we showed that one can achieve (inefficient) SNARKs under knowledge assumptions. My 2003 paper on using Diophantine equations and groups of unknown order and my 2012 paper on trustless accumulators inspired well-known SNARKs like DARK. My 2012 paper on SNARKs was the last "theoretical" step before GGPR13 and Pinocchio made SNARKs practical. In 2017, I got the best (or best-3) paper award in Asiacrypt for our paper that defined and constructed subversion-resistant SNARKs. In 2022, I had one paper where I generalized Groth16-like SNARKs to many settings and another paper where we proposed the most communication-efficient known updatable SNARK Vampire.

News

See the news section in the research group page.

Previous Ph.D. Students

• Sven Laur (Ph.D. 2008, now an associate professor at the University of Tartu) - google scholar 

• Bingsheng Zhang (Ph.D. 2012,  now a professor at Zhejiang University) - google scholar

• Prastudy Fauzi (Ph.D. 2017, now a research fellow at Nanjiang Technical University) - google scholar 

• Rafik Chaabouni (Ph.D. 2017, now a cyber security architect at Swiss Armed Forces) - google scholar 

• Janno Siim (Ph.D. 2020, now a postdoc at Simula UiB) - google scholar 

• Karim Baghery (Ph.D. 2020, now a postdoc at KU Leuven) - google scholar 

• Behzad Abdolmaleki (Ph.D. 2020, now an assistant professor at the University of Sheffield) - google scholar 

• Arne-Tobias Ødegaard (Ph.D. 2022, now a postdoc at NSM) - google scholar

• Roberto Parisella (Ph.D. 2023, now a postdoc at Simula UiB) - google scholar

Previous Honorary Ph.D. Students

(People who had a different supervisor but who spent a considerable amount of time in my research group as a Ph.D. student)

• Michal Zajac (now a head of cryptography research at Nethermind) - google scholar

• Toomas Krips (now an assistant professor at University of Tartu) - google scholar