Konstantinos (Kostas) Chalkias

Research Scientist

I hold a PhD in identity-based encryption, and am a cryptographer at Novi, focusing on privacy-preserving protocols and contributing to the Diem (formerly Libra) project’s crypto API. Before joining Novi, I was the lead cryptographer at R3, one of the biggest blockchain banking consortia, mainly dealing with secure smart contracts for finance. Prior to that, I was the CTO of two security and machine learning startups (Erybo and Safemarket), where I built a platform for fair and secure national exams and quiz platforms using time-lapse cryptography. My fields of expertise include timed-release encryption, auditing protocols, secure enclaves, graphical passwords, and post-quantum cryptography. I also implemented and found critical bugs in a number of smart contracts in the past, such as atomic swaps and multi-party apps on blockchain, including decentralized lotteries, lightning chess, and card games.


Cryptograpic schemes and attacks: zero knowledge proofs, post-quantum, SGX, timed-release encryption, graphical passwords, biometrics, distributed randomness

Latest Publications

PETS - July 16, 2021

HashWires: Hyperefficient Credential-Based Range Proofs

Konstantinos (Kostas) Chalkias, Shir Cohen, Kevin Lewi, Fredric Moezinia, Yolan Romailler

Trusted Smart Contracts Workshop at Financial Cryptography (FC) - May 12, 2021

Reactive Key-Loss Protection in Blockchains

Sam Blackshear, Konstantinos (Kostas) Chalkias, Panagiotis Chatzigiannis, Riyaz Faizullabhoy, Irakliy Khaburzaniya, Lefteris Kokoris Kogias, Joshua Lind, David Wong, Tim Zakian

SSR - October 22, 2020

Taming the many EdDSAs

Konstantinos (Kostas) Chalkias, François Garillot, Valeria Nikolaenko

ZKProof - April 22, 2020

Distributed Auditing Proofs of Liabilities

Konstantinos (Kostas) Chalkias, Kevin Lewi, Payman Mohassel, Valeria Nikolaenko

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