Ran Cohen

Principal Research Scientist

Cybersecurity and Privacy Institute
Khoury College of Computer Sciences
Northeastern University
Email: rancohen@ccs.neu.edu

I am a principal research scientist at the Khoury College of Computer Sciences at Northeastern University.

Prior to that, I spent two great years as a post-doctoral researcher in the Boston area, working with Shafi Goldwasser at MIT CSAIL, with abhi shelat at Northeastern University, and with Ran Canetti at Boston University, and one year at Tel Aviv University working with Iftach Haitner.
I completed my Ph.D. in 2016 working at the Cryptography Research Group at Bar-Ilan University, where I was very fortunate to have Yehuda Lindell as my advisor.
I received my M.Sc. from the Department of Mathematics at Bar-Ilan University under the supervision of Boris Kunyavskii.

My research interests are in cryptography and its synergy with distributed computing, mainly focusing on secure multiparty computation and consensus protocols.

TCC 2020 - The 18th Theory of Cryptography Conference
EUROCRYPT 2020 - The 39th Annual International Conference on the Theory and Applications of Cryptographic Techniques
PODC 2020 - The 39th ACM Symposium on Principles of Distributed Computing
CANS 2020 - The 18th International Conference on Cryptology and Network Security
INDOCRYPT 2020 - The 21st International Conference on Cryptology in India
TCC 2019 - The 17th Theory of Cryptography Conference

(see dblp and Google Scholar)

Breaking the \(O(\sqrt{n})\)-Bits Barrier: Byzantine Agreement with Polylog Bits Per-Party
Elette Boyle, Ran Cohen, and Aarushi Goel
- Manuscript 2020
- Preliminary full version [eprint] [arxiv]

On the Power of an Honest Majority in Three-Party Computation Without Broadcast
Bar Alon, Ran Cohen, Eran Omri, and Tom Suad
- TCC 2020 - 18th Theory of Cryptography Conference [link]
- Preliminary full version [eprint]
- [slides] [video] (by Bar)

Topology-Hiding Communication from Minimal Assumptions
Marshall Ball, Elette Boyle, Ran Cohen, Lisa Kohl, Pierre Meyer, Tal Malkin, and Tal Moran
- TCC 2020 - 18th Theory of Cryptography Conference [link]
- Preliminary full version [link]
- [slides] [short video] [video] (by Pierre)

Multiparty Generation of an RSA Modulus
Megan Chen, Ran Cohen, Jack Doerner, Yashvanth Kondi, Eysa Lee, Schuyler Rosefield, and abhi shelat
- CRYPTO 2020 - 40th Annual International Cryptology Conference [link]
- Preliminary full version [eprint]
- [video] (by Jack)

Broadcast-Optimal Two-Round MPC
Ran Cohen, Juan Garay, and Vassilis Zikas
- EUROCRYPT 2020 - 39th Annual International Conference on the Theory and Applications of Cryptographic Techniques [link]
- Preliminary full version [eprint]
- [slides] [video]

Adaptively Secure MPC with Sublinear Communication Complexity
Ran Cohen, abhi shelat, and Daniel Wichs
- CRYPTO 2019 - 39th Annual International Cryptology Conference [link]
- Preliminary full version [eprint]
- [slides] [video] (by abhi)

Is Information-Theoretic Topology-Hiding Computation Possible?
Marshall Ball, Elette Boyle, Ran Cohen, Tal Malkin, and Tal Moran
- TCC 2019 - 17th Theory of Cryptography Conference [link]
- Preliminary full version [eprint]
- [slides] [video]

On the Round Complexity of Randomized Byzantine Agreement
Ran Cohen, Iftach Haitner, Nikolaos Makriyannis, Matan Orland, and Alex Samorodnitsky
- DISC 2019 - 33rd International Symposium on Distributed Computing [link]
- Preliminary full version [eprint] [arxiv]
- [slides] [short video] (by Nikos)

Must the Communication Graph of MPC Protocols be an Expander?
Elette Boyle, Ran Cohen, Deepesh Data, and Pavel Hubacek
- CRYPTO 2018 - 38th Annual International Cryptology Conference [link]
- Preliminary full version [eprint]
- [slides] [short video] [video]

From Fairness to Full Security in Multiparty Computation
Ran Cohen, Iftach Haitner, Eran Omri, and Lior Rotem
- SCN 2018 - 11th International Conference on Security and Cryptography for Networks [link]
- Preliminary full version [eprint]
- [slides]

Round-Preserving Parallel Composition of Probabilistic-Termination Cryptographic Protocols
Ran Cohen, Sandro Coretti, Juan Garay, and Vassilis Zikas
- Journal of Cryptology, 2021 (to appear)
- ICALP 2017 - 44th International Colloquium on Automata, Languages, and Programming [link]
- Preliminary full version [eprint]
- [slides]

Probabilistic Termination and Composability of Cryptographic Protocols
Ran Cohen, Sandro Coretti, Juan Garay, and Vassilis Zikas
- Journal of Cryptology, 2019 [link]
- CRYPTO 2016 - 36th Annual International Cryptology Conference [link]
- Full version [eprint]
- [slides] [video]

Asynchronous Secure Multiparty Computation in Constant Time
Ran Cohen
- PKC 2016 - 19th International Conference on Practice and Theory in Public-Key Cryptography [link]
- Preliminary full version [eprint]
- [slides]

Characterization of Secure Multiparty Computation Without Broadcast
Ran Cohen, Iftach Haitner, Eran Omri, and Lior Rotem
- Journal of Cryptology, 2018 [link]
- TCC 2016-A - 13th Theory of Cryptography Conference [link]
- Full version [eprint]
- [slides] [video]

On Adaptively Secure Multiparty Computation with a Short CRS
Ran Cohen and Chris Peikert
- SCN 2016 - 10th International Conference on Security and Cryptography for Networks [link]
- Preliminary full version [eprint]
- [slides]

Fairness versus Guaranteed Output Delivery in Secure Multiparty Computation
Ran Cohen and Yehuda Lindell
- Journal of Cryptology, 2017 [link]
- ASIACRYPT 2014 - 20th International Conference on the Theory and Application of Cryptology and Information Security [link]
- Full version [eprint]
- [slides]

Group Law Algorithms for Jacobian Varieties of Curves over Finite Fields
Ran Cohen
- Algebraic Geometry and Its Applications, volume 5 of Number Theory and its Applications, 2008 [link]
- Preliminary full version [PDF]

Studies on Full Security in Multiparty Computation
Ran Cohen
- Ph.D. Dissertation, Bar-Ilan University, 2017 [PDF]

Some of my talks have been filmed and can be found online:

Broadcast-Optimal Two-Round MPC (22 minutes), EUROCRYPT 2020, virtual, May, 2020
Is Information-Theoretic Topology-Hiding Computation Possible? (56 minutes), BIU Seminar, April, 2020
Probabilistic Termination and Composability of Cryptographic Protocols (28 minutes), Workshop on Usable, Efficient, and Formally Verified Secure Computation, BU, March, 2019
Must the Communication Graph of MPC Protocols be an Expander? (20 minutes), CRYPTO 2018, UCSB, August, 2018
Applying Modern Crypto to Advance Social Science (38 minutes), Differential Privacy Meets Multi-Party Computation (DPMPC) Workshop, BU, June, 2018
Must the Communication Graph of MPC Protocols be an Expander? (3 minutes), rump session of EUROCRYPT 2018, Tel-Aviv, April, 2018
Probabilistic Termination and Composability of Cryptographic Protocols (25 minutes), CRYPTO 2016, UCSB, August, 2016
Characterization of Secure Multiparty Computation Without Broadcast (22 minutes), TCC 2016-A, Tel-Aviv, January, 2016.

Cryptography, Northeastern University, Spring 2021, [link]
Introduction to Cybersecurity (with abhi shelat), Northeastern University, Fall 2020, [link]
Seminar on Secure Multi-Party Computation (with Iftach Haitner), Tel Aviv University, 2017, [link]
Discrete Mathematics, Bar-Ilan University, 2011-2016 (teaching assistant)
Volunteered at the program for talented youth in mathematics, Bar-Ilan University, 2015