Sebastian Ramacher

I am a scientist in the Cryptography group at AIT Austrian Institute of Technology in Vienna, Austria. Before joining AIT, I was a postdoc working in the Cryptology and Cryptographic Security at IAIK, Graz University of Technology and received a PhD degree with distinction from Graz University of Technology in 2019. My main research interests are in the field of public key cryptography with a focus on post-quantum signature schemes and modern public key cryptography. I am a member of the International Association for Cryptologic Research (IACR) and the Austrian Mathematical Society (ÖMG).

Publications and Talks

Conferences and Journals

2020 Lukas Alber, Stefan More, Sebastian Ramacher. Short-Lived Forward-Secure Delegation for TLS. CCSW 2020
2020 Valerio Cini, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks. CCA Secure (Puncturable) KEMs from Encryption With Non-Negligible Decryption Errors. accepted at Asiacrypt 2020
2020 Behzad Abdolmaleki, Sebastian Ramacher, Daniel Slamanig. Lift-and-Shift: Obtaining Simulation Extractable Subversion and Updatable SNARKs Generically. CCS 2020
2020 Daniel Kales, Sebastian Ramacher, Christian Rechberger, Roman Walch, Mario Werner. Efficient FPGA Implementations of LowMC and Picnic. CT-RSA 2020
2019 Andreas Abraham, Felix Hörandner, Olamide Omolola, Sebastian Ramacher. Privacy-Preserving eID Derivation for Self-Sovereign Identity Systems. ICICS 2019
2019 Felix Hörandner, Sebastian Ramacher, Simon Roth. Selective End-To-End Data-Sharing in the Cloud. ICISS 2019
2019 Martin R. Albrecht, Lorenzo Grassi, Léo Perrin, Sebastian Ramacher, Christian Rechberger, Dragos Rotaru, Arnab Roy, Markus Schofnegger. Feistel Structures for MPC, and More. Esorics 2019
2019 Daniel Kales, Olamide Omolola, Sebastian Ramacher. Revisting User Privacy for Certificate Transparency. EuroS&P 2019
2019 Itai Dinur, Daniel Kales, Angela Promitzer, Sebastian Ramacher, Christian Rechberger. Linear Equivalence of Block Ciphers with Partial Non-Linear Layers: Application to LowMC. Eurocrypt 2019
2018 David Derler, Sebastian Ramacher, Daniel Slamanig. Generic Double-Authentication Preventing Signatures and a Post-Quantum Instantiation. ProvSec 2018
2018 David Derler, Sebastian Ramacher, Daniel Slamanig. Post-Quantum Zero-Knowledge Proofs for Accumulators with Applications to Ring Signatures from Symmetric-Key Primitives. PQCrypto 2018
2018 David Derler, Stephan Krenn, Thomas Lorünser, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks. Revisiting Proxy Re-Encryption: Forward Secrecy, Improved Security and Applications. PKC 2018
2018 David Derler, Sebastian Ramacher, Daniel Slamanig. Short Double- and N-Times-Authentication-Preventing Signatures from ECDSA and More. EuroS&P 2018
2017 Melissa Chase, David Derler, Steven Goldfeder Claudio Orlandi, Sebastian Ramacher, Christian Rechberger, Daniel Slamanig, Greg Zaverucha. Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives. CCS 2017
2017 David Derler, Sebastian Ramacher, Daniel Slamanig. Homomorphic Proxy Re-Authenticators and Applications to Verifiable Multi-User Data Aggregation. FC 2017.
2015 Alfred Geroldinger, Sebastian Ramacher, Andreas Reinhart. On v-Marot Mori rings and C-rings. Journal of the Korean Mathematical Society Vol. 52 No. 1/2015

Preprints

2020 Lukas Helminger, Daniel Kales, Sebastian Ramacher, Roman Walch. Multi-Party Revocation in Sovrin: Performance through Distributed Trust.
2019 David Derler, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks. I Want to Forget: Fine-Grained Encryption with Full Forward Secrecy in the Distributed Setting
2017 Daniel Kales, Léo Perrin, Angela Promitzer, Sebastian Ramacher, Christian Rechberger. Improvements to the Linear Layer of LowMC: A Faster Picnic
2016 David Derler, Claudio Orlandi, Sebastian Ramacher, Christian Rechberger, Daniel Slamanig. Digital Signatures from Symmetric-Key Primitives

Talks

2020 Lift-and-Shift: Obtaining Simulation Extractable Subversion and Updatable SNARKs Generically at Young Researcher Crypto Seminar (organized by TU Darmstadt)
2020 Lift-and-Shift: Obtaining Simulation Extractable Subversion and Updatable SNARKs Generically at Graz University of Technology
2019 Future-Proof Communication Security at the Industry Track of the Graz Security Week 2019 (together with Daniel Slamanig and Christoph Striecks)
2019 Revisting User Privacy for Certificate Transparency at EuroS&P 2019
2018 Generic Double-Authentication Preventing Signatures and a Post-Quantum Instantiation at ProvSec 2018.
2018 Post-Quantum Zero-Knowledge Proofs for Accumulators with Applications to Ring Signatures from Symmetric-Key Primitives at PQCrypto 2018.
2018 Short Double- and N-Times-Authentication-Preventing Signatures from ECDSA and More at EuroS&P 2018.
2017 Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives at CCS 2017 on November 2, 2017 (together with Steven Goldfeder).
2017 Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives at Microsoft Research on October 26, 2017.
2017 Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives at CryptoSymposium 2017 on March 28, 2017.

NIST PQC Competition: Picnic

The Picnic family of digital signature algorithms is designed to provide security against attacks by quantum computers, in addition to attacks by classical computers. The building blocks are a zero-knowledge proof system (with post-quantum security), and symmetric key primitives like hash functions and block ciphers, with well-understood post-quantum security. Picnic is an Alternate Candiate in round 3 of the ongoing NIST PQC effort.

An implementation optimized for performance is available on GitHub. Packages for Ubuntu are available on my Ubuntu PPA. Python bindings for this implementation are available via PyPI and the PPA.

Projects

Upcoming/Ongoing:

  • FFG KIRAS ROUTE (2020-2021)
  • EU Horizon 2020 KRAKEN (2019-2022)

Past:

Other Activities

External Reviewer for International Conferences

ACM CCS 2020; IFIP SEC 2020; PKC 2020; ICISC 2020, 2019, 2016; Eurocrypt 2019, 2017; MACIS 2019; IMA CC 2019; IFIP Summer School 2019; Africacrypt 2019, 2016; ACNS 2018; APKC 2018; CT-RSA 2018; ICDCS 2018; Asiacrypt 2017, 2016; SECPID 2017

Teaching

While at Graz University of Technology, I was involved with the following courses:

I also had the pleasure to (co-)supervise various bachelor’s and master’s thesis:

If you are interested in a bachelor’s or master’s thesis in post-quantum or public-key cryptography, feel free to contact me.

Open Source

For my work on Debian and open source software, see my projects page.