Stefan Kölbl

Information Security Engineer

Google

Biography

I am a cryptographer working at Google in the information security engineering team. Before, I have been the Senior Technology Manager at Cybercrypt.

After I obtained my PhD degree, I have been a postdoctoral researcher in the Cyber Security group at the Technical University of Denmark working on the H2020 PQCRYPTO project. I did my PhD under the supervision of Christian Rechberger and Lars Knudsen at DTU Compute, Technical University of Denmark, working on the design and analysis of symmetric key cryptographic algorithms.

Interests

  • Post-quantum Cryptography
  • Cryptographic Hash Functions and Block Ciphers
  • Secure and Efficient Implementations
  • Tools for Cryptanalysis

Education

  • PhD in Cryptology, 2016

    Technical University of Denmark

  • MSc in Computer Science, 2013

    Graz University of Technology

  • BSc in Computer Science, 2011

    Graz University of Technology

Services

Program Committee

Conference Refereeing

  • 2022: Crypto, FSE
  • 2021: FSE, PQCrypto
  • 2020: CHES, FSE
  • 2019: FSE, Latincrypt, PQCrypto
  • 2018: Asiacrypt, Designs, Codes and Cryptography, FSE, IET Information Security, Transactions on Computers, The Computer Journal, PQCrypto
  • 2017: Africacrypt, FSE, IET Information Security, PQCrypto
  • 2016: ACNS, Crypto, FSE, IET Information Security, Journal of Cryptographic Engineering
  • 2015: Asiacrypt, Eurocrypt, FSE, IET Information Security, Indocrypt, CT-RSA, SAC, ISISC
  • 2014: ACNS, Asiacrypt, CANS, FSE

Standardization

Representative of Switzerland for ISO/IEC JTC 1 SC 27 (IT Security techniques) Work Group 2 (Cryptography and security mechanisms) from 2020 to now.

Representative of Denmark for ISO/IEC JTC 1 SC 27 (IT Security techniques) Work Group 2 (Cryptography and security mechanisms) from 2017 to 2019.

Projects

CryptoSMT

A tool for automating differential cryptanalysis for cryptographic primitives.

Gimli

A cryptographic permutation designed for high performance. Gimli is part of the NIST Lightweight Project and is part of LibHydrogen.

Haraka

A short-input hash function optimized for high performance on platforms supporting AES-NI. Used in SPHINCS+ and Gravity-SPHINCS.

Pyjamask

A cipher designed for efficient software implementations with strong side-channel protections submitted to the NIST Lightweight Project …

Skinny

A lightweight tweakable block cipher with strong security guarantees. Submitted to the NIST Lightweight Project.

SPHINCS+

A digital signature scheme submitted to the NIST Post-Quantum Project.

Publications

How to Abuse and Fix Authenticated Encryption Without Key Commitment

Authenticated encryption (AE) is used in a wide variety of applications, potentially in settings for which it was not originally …
Ange Albertini, Thai Duong, Shay Gueron, Stefan Kölbl, Atul Luykx, Sophie Schmieg
PDF

The SPHINCS+ Signature Framework

We introduce SPHINCS+, a stateless hash-based signature framework. SPHINCS+ has significant advantages over the state of the art in …
Daniel J. Bernstein, Andreas Hülsing, Stefan Kölbl, Ruben Niederhagen, Joost Rijneveld, Peter Schwabe
PDF

Finding Integral Distinguishers with Ease

The division property method is a technique to determine integral distinguishers on block ciphers. While the complexity of finding …
Zahra Eskandari, Andreas Brasen Kidmose, Stefan Kölbl, Tyge Tiessen
PDF Code

Gimli: a cross-platform permutation

This paper presents Gimli, a 384-bit permutation designed to achieve high security with high performance across a broad range of …
Daniel J. Bernstein, Stefan Kölbl, Stefan Lucks, Pedro Maat Costa Massolino, Florian Mendel, Kashif Nawaz, Tobias Schneider, Peter Schwabe, François-Xavier Standaert, Yosuke Todo, Benoît Viguier, Tomsilav Nad
PDF Code Slides

The SKINNY Family of Block Ciphers and its Low-Latency Variant MANTIS

We present a new tweakable block cipher family SKINNY, whose goal is to compete with NSA recent design SIMON in terms of …
Christof Beierle, Jérémy Jean, Stefan Kölbl, Gregor Leander, Amir Moradi, Thomas Peyrin, Yu Sasaki, Pascal Sasdrich, Siang Meng Sim
PDF Code Slides
See all publications

Talks

ShiftRows Alternatives for AES-like Ciphers and Optimal Cell Permutations for Midori and Skinny
Mar 2019 FSE 2019 Paris
Post-quantum Cryptography
May 2018 Dansk Standard Copenhagen
Update on the PQCrypto Project
Apr 2018 ISO/IEC JTC1 SC27 Wuhan
Putting Wings on SPHINCS
Apr 2018 PQCrypto 2018 Fort Lauderdale, FL
How to instantiate Hash-based Signatures?
Jan 2018 Combined event on Post-Quantum Cryptography Tenerife
See all talks

Contact