Igors Stepanovs

I am interested in practice-oriented cryptography.

I currently have no affiliation. Previously I worked as a postdoctoral researcher with Kenny Paterson in the Applied Cryptography Group at ETH Zürich. I earned a PhD in Computer Science at University of California, San Diego advised by Mihir Bellare. Prior to starting my PhD studies, I obtained BSc and MSc in Computer Science at University of Latvia, and MSc in Mathematics of Cryptography and Communcations at Royal Holloway, University of London.

My interest in computer science was sparked by programming olympiads during my school years. They combine algorithmic problem solving with proof-of-concept implementations, thus showcasing transitions from theoretical ideas to practical implementations. I was drawn to the idea of working at the boundary between the two worlds. I found that cryptography is an area that presents a lot of exciting and relevant work at the intersection of theory and practice. Along the way, I tried my hand at a number of adjacent jobs in the private sector, including part-time and full-time positions as a software developer and a researcher in a company that provides software code protection, and a system analyst in banking. You can find more details in my CV.

Papers

Four Attacks and a Proof for Telegram (webpage)
Martin R. Albrecht, Lenka Mareková, Kenneth G. Paterson, Igors Stepanovs. IEEE S&P 2022 (Distinguished Paper Award).
my slides from the Joint Latvian-Estonian Theory Days 2022; my online talk and slides from RWC 2022; my comments in popular press.

Security under Message-Derived Keys: Signcryption in iMessage
Mihir Bellare, Igors Stepanovs. EUROCRYPT 2020.
my pre-recorded talk and slides.

On the Security of Two-Round Multi-Signatures
Manu Drijvers, Kasra Edalatnejad, Bryan Ford, Eike Kiltz, Julian Loss, Gregory Neven, Igors Stepanovs. IEEE S&P 2019.
talk by Manu Drijvers.

Optimal Channel Security Against Fine-Grained State Compromise: The Safety of Messaging
Joseph Jaeger, Igors Stepanovs. CRYPTO 2018.
talk by Joseph Jaeger.

Forward-Security under Continual Leakage
Mihir Bellare, Adam O'Neill, Igors Stepanovs. CANS 2017.

Ratcheted Encryption and Key Exchange: The Security of Messaging
Mihir Bellare, Asha Camper Singh, Joseph Jaeger, Maya Nyayapati, Igors Stepanovs. CRYPTO 2017.
talk by Joseph Jaeger.

New Negative Results on Differing-Inputs Obfuscation
Mihir Bellare, Igors Stepanovs, Brent Waters. EUROCRYPT 2016.
my (truncated) talk and slides.

Contention in Cryptoland: Obfuscation, Leakage and UCE
Mihir Bellare, Igors Stepanovs, Stefano Tessaro. TCC 2016-A.
talk by Stefano Tessaro at the Simons Workshop on Securing Computation in June 2015; my slides (combined for two papers) from TCC 2016-A.

Point-Function Obfuscation: A Framework and Generic Constructions
Mihir Bellare, Igors Stepanovs. TCC 2016-A.
my slides (combined for two papers).

Poly-Many Hardcore Bits for Any One-Way Function and a Framework for Differing-Inputs Obfuscation
Mihir Bellare, Igors Stepanovs, Stefano Tessaro. ASIACRYPT 2014.
my slides.

Advising and Service

Advising: Tijana Klimovic (MSc thesis, Mar 2021 – Sep 2021). Modular Design of the Messaging Layer Security (MLS) Protocol. Co-Advisor: Kenneth G. Paterson. ETH Zürich, Switzerland.

Program Committee (PC) Memberships: PKC 2022.

Peer Review for Scientific Conferences: CRYPTO 2015, EUROCRYPT 2017, ICALP 2017, CRYPTO 2017, MFCS 2017, TCC 2019, PKC 2020, CRYPTO 2020, ASIACRYPT 2020, CRYPTO 2021, CRYPTO 2022.

Miscellaneous

Relations Between Obfuscation Notions
Igors Stepanovs. A diagram showing the context and connections between the core results from our TCC 2016-A and EUROCRYPT 2016 papers.

A technical description and a toy implementation of an LWE-based FHE scheme.
Igors Stepanovs. Project for UC San Diego class CSE206A in 2014 taught by Daniele Micciancio. The scheme was defined in class and is roughly based on GSW13, BV14, AP14.

Survey of Fully Homomorphic Encryption
Igors Stepanovs. MSc dissertation, Royal Holloway, University of London, 2012.

Query Complexity of Boolean Functions with Low Polynomial Degree (in Latvian)
Igors Stepanovs. MSc thesis, University of Latvia, 2012.
my slides from the Joint Estonian-Latvian Theory Days 2012.

Query Complexity of Boolean Functions with Low Polynomial Degree (in Latvian)
Igors Stepanovs. BSc thesis, University of Latvia, 2010.