Sebastian Ramacher¶
I am a Senior 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¶
2024 |
Lena Heimberger, Tobias Hennerbichler, Fredrik Meisingseth, Sebastian Ramacher, Christian Rechberger. OPRFs from Isogenies: Designs and Analysis. ACM AsiaCCS 2024 (accepted) |
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2024 |
Behzad Abdolmaleki, Noemi Glaeser, Sebastian Ramacher, Daniel Slamanig. Circuit-Succinct Universally-Composable NIZKs with Updatable CRS. IEEE CSF 2024 (accepted) |
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2023 |
Valerio Cini, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks, Erkan Tairi. (Inner-Product) Functional Encryption with Updatable Ciphertexts. Journal of Cryptology |
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2023 |
Christian Göth, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks, Erkan Tairi, Alexander Zikulnig. Optimizing 0-RTT Key Exchange with Full Forward Security. CCSW 2023 |
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2023 |
Christoph Döberl, Wolfgang Eibner, Simon Gärtner, Manuela Kos, Florian Kutschera, Sebastian Ramacher. Quantum-resistant End-to-End Secure Messaging and Email Communication. SECPID @ ARES 2023 |
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2023 |
Paul James, Stephan Laschet, Sebastian Ramacher, Luca Torresetti. Key Management Systems for Large-Scale Quantum Key Distribution Networks. SECPID @ ARES 2023 |
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2023 |
Sonja Bruckner, Sebastian Ramacher, Christoph Striecks. Muckle+: End-to-End Hybrid Authenticated Key Exchanges. PQCrypt 2023 |
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2022 |
Karl Koch, Stephan Krenn, Tilen Marc, Stefan More, Sebastian Ramacher. KRAKEN: A Privacy-Preserving Data Market for Authentic Data. ACM Data Economy Workshop 2022 |
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2022 |
Stefan More, Sebastian Ramacher, Lukas Alber, Marco Herzl. Extending Expressive Access Policies with Privacy Features. TrustCom 2022 |
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2021 |
Jan Bobolz, Fabian Eidens, Stephan Krenn, Sebastian Ramacher, Kai Samelin. Issuer-Hiding Attribute-Based Credentials. CANS 2021 |
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2021 |
Omar Veledar, Eric Armengaud, Leo Happ Botler, Violeta Damjanovic-Behrendt, Christian Derler, Stefan Jaksic, Lukas Krammer, Christian Lettner, Georg Macher, Stefan Marksteiner, Andreas Martin, Martin Matschnig, Peter Priller, Sebastian Ramacher, Kay Römer, Christoph Schmittner, Christina Tiefnig, Heribert Vallant, Heinz Weiskirchner, Mario Drobics. Steering Drivers of Change: Maximising Benefits of Trustworthy IoT. EuroSPI 2021 |
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2021 |
Sebastian Ramacher, Daniel Slamanig, Andreas Weninger. Privacy-Preserving Authenticated Key Exchange: Stronger Privacy and Generic Constructions. Esorics 2021 |
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2021 |
Andreas Abraham, Karl Koch, Stefan More, Sebastian Ramacher, Miha Stopar. Privacy-Preserving eID Derivation to Self-Sovereign Identity Systems with Offline Revocation. TrustCom 2021 |
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2021 |
Lukas Helminger, Daniel Kales, Sebastian Ramacher, Roman Walch. Multi-Party Revocation in Sovrin: Performance through Distributed Trust. CT-RSA 2021 |
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2021 |
Valerio Cini, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks, Erkan Tairi. Updatable Signatures and Message Authentication Codes. PKC 2021 |
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2021 |
David Derler, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks. Fine-Grained Forward Secrecy: Allow-List/Deny-List Encryption and Applications. FC 21 |
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2020 |
Karl Koch, Stephan Krenn, Donato Pellegrino and Sebastian Ramacher Privacy-preserving Analytics for Data Markets using MPC. IFIP Summer School 2020 |
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2020 |
Lukas Alber, Stefan More, Sebastian Ramacher. Short-Lived Forward-Secure Delegation for TLS. CCSW 2020 |
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2020 |
Valerio Cini, Sebastian Ramacher, Daniel Slamanig, Christoph Striecks. CCA Secure (Puncturable) KEMs from Encryption With Non-Negligible Decryption Errors. Asiacrypt 2020 |
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2020 |
Behzad Abdolmaleki, Sebastian Ramacher, Daniel Slamanig. Lift-and-Shift: Obtaining Simulation Extractable Subversion and Updatable SNARKs Generically. CCS 2020 |
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2020 |
Daniel Kales, Sebastian Ramacher, Christian Rechberger, Roman Walch, Mario Werner. Efficient FPGA Implementations of LowMC and Picnic. CT-RSA 2020 |
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2019 |
Andreas Abraham, Felix Hörandner, Olamide Omolola, Sebastian Ramacher. Privacy-Preserving eID Derivation for Self-Sovereign Identity Systems. ICICS 2019 |
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2019 |
Felix Hörandner, Sebastian Ramacher, Simon Roth. Selective End-To-End Data-Sharing in the Cloud. ICISS 2019 |
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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 |
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2019 |
Daniel Kales, Olamide Omolola, Sebastian Ramacher. Revisting User Privacy for Certificate Transparency. EuroS&P 2019 |
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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 |
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2018 |
David Derler, Sebastian Ramacher, Daniel Slamanig. Generic Double-Authentication Preventing Signatures and a Post-Quantum Instantiation. ProvSec 2018 |
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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 |
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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 |
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2018 |
David Derler, Sebastian Ramacher, Daniel Slamanig. Short Double- and N-Times-Authentication-Preventing Signatures from ECDSA and More. EuroS&P 2018 |
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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 |
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2017 |
David Derler, Sebastian Ramacher, Daniel Slamanig. Homomorphic Proxy Re-Authenticators and Applications to Verifiable Multi-User Data Aggregation. FC 2017. |
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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¶
2017 |
Daniel Kales, Léo Perrin, Angela Promitzer, Sebastian Ramacher, Christian Rechberger. Improvements to the Linear Layer of LowMC: A Faster Picnic |
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2016 |
David Derler, Claudio Orlandi, Sebastian Ramacher, Christian Rechberger, Daniel Slamanig. Digital Signatures from Symmetric-Key Primitives |
Talks¶
2024 |
Muckle+: End-to-End Authenticated Key Exchanges at QSNP Workshop Quantum Meets Classical Cryptography on January 10, 2024. |
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2023 |
Optimizing 0-RTT Key Exchange with Full Forward Security. at CCSW 2023 on November 26, 2023. |
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2021 |
Fine-Grained Forward Secrecy: Allow-List/Deny-List Encryption and Applications at FC 21 on March 4, 2021 (together with Daniel Slamanig and Christoph Striecks). |
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2020 |
Lift-and-Shift: Obtaining Simulation Extractable Subversion and Updatable SNARKs Generically at Young Researcher Crypto Seminar (organized by TU Darmstadt) |
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2020 |
Lift-and-Shift: Obtaining Simulation Extractable Subversion and Updatable SNARKs Generically at Graz University of Technology |
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2019 |
Future-Proof Communication Security at the Industry Track of the Graz Security Week 2019 (together with Daniel Slamanig and Christoph Striecks) |
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2019 |
Revisting User Privacy for Certificate Transparency at EuroS&P 2019 |
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2018 |
Generic Double-Authentication Preventing Signatures and a Post-Quantum Instantiation at ProvSec 2018. |
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2018 |
Post-Quantum Zero-Knowledge Proofs for Accumulators with Applications to Ring Signatures from Symmetric-Key Primitives at PQCrypto 2018. |
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2018 |
Short Double- and N-Times-Authentication-Preventing Signatures from ECDSA and More at EuroS&P 2018. |
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2017 |
Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives at CCS 2017 on November 2, 2017 (together with Steven Goldfeder). |
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2017 |
Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives at Microsoft Research on October 26, 2017. |
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2017 |
Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives at CryptoSymposium 2017 on March 28, 2017. |
Non-scientific Publications¶
2023 |
Stephan Krenn, Thomas Lorünser, Sebastian Ramacher, Florian Wohner. Outsourced Computations Maintaining Confidentiality and Authenticity ERCIM News 2023 (133) |
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2022 |
Silvia Gabrielli, Stephan Krenn, Donato Pellegrino, Juan Carlos Pérez Baún, Pilar Pérez Berganza, Sebastian Ramacher, Wim Vandevelde. KRAKEN: A Secure, Trusted, Regulatory-Compliant, and Privacy-Preserving Data Sharing Platform Data Spaces |
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2021 |
Andreas Abraham, Juan Carlos Perez Braun, Sebastian Ramacher. KRAKEN - Brokerage and Market Platform for Personal Data. ERCIM News 2021 (126) |
Blog Posts¶
Daniel Slamanig and Christoph Striecks and myself wrote a three part series on puncturable encryption titled Puncturable Encryption – A Fine-Grained Approach to Forward-Secure Encryption and More. The series covers motivation, constructions, applications and implementations of puncturable encryption. All parts – Part I, Part II, and Part III – are already available.
NIST PQC Competition: FAEST¶
FAEST is a digital signature algorithm designed to be secure against quantum computers. The security of FAEST is based on standard cryptographic hashes and ciphers, specifically SHA3 and AES, which are believed to remain secure against quantum adversaries.
The reference implementation is available on GitHub. Packages for Ubuntu are available from my Ubuntu PPA.
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. Rust bindings are available as well.
Open Source Implementations¶
Over the years, I have implemented various protocols and other tools to support the various research projects. Below is an incomplete list of these implementations:
pyrelic: a wrapper for relic for easy prototyping in Python.
bfe: an implementation of Bloom filter encryption based on the Boneh-Franklin IBE and time-based Bloom filter encryption using the Boneh-Boyen-Goh HIBE.
isap-aead: a Rust implementation of the ISAP authenticated encryption scheme.
ascon-aead: a Rust implementation of the Ascon authenticated encryption scheme and hash function.
Projects¶
Upcoming/Ongoing:
DEP QCI-CAT (2023-2025)
Past:
EU Horizon 2020 KRAKEN (2019-2022)
FFG KIRAS ROUTE (2020-2021)
IoT4CPS (2018-2020)
EU Horizon 2020 Safe-DEED (2018-2019)
EU Horizon 2020 CREDENTIAL (2015-2018)
EU Horizon 2020 PRISMACLOUD (2015-2018)
Other Activities¶
Program Committee¶
SECPID @ ARES 2023 (PC chair)
SECPID @ ARES 2022 (PC chair)
External Reviewer for International Conferences¶
ACISP 2022; ACM CCS 2022, 2021, 2020; ACNS 2024, 2018; APKC 2018; Africacrypt 2019, 2016; Asiacrypt 2021, 2017, 2016; CT-RSA 2018; Eurocrypt 2023, 2019, 2017; ICDCS 2018; ICISC 2021 2020, 2019, 2016; ICISSP 2021; IFIP SEC 2022, 2021, 2020; IFIP Summer School 2019; IMA CC 2019; ISC 2023; IWSEC 2021; MACIS 2019; PKC 2020; SECPID 2017
Reviewer for Journals¶
IEEE Transactions on Information Forensics & Security;
Teaching¶
While at Graz University of Technology, I was involved with the following courses:
Modern Public Key Cryptography (2017 ST, 2018 ST, 2019 ST)
IT Security (2016 ST, 2016 WT, 2017 WT, 2018 WT)
I also had the pleasure to (co-)supervise various bachelor’s and master’s thesis:
Angela Promitzer: Efficient Picnic: Optimizing a Post-Quantum Signature Scheme (awarded a WKO-Forschungsstipendium)
Markus Schofnegger: Implementing and Optimizing Lightweight Block Ciphers in the Context of a Signature Scheme
Dominik Schreilechner: Extended Functionality of Cryptographic Protocols in Bitcoin
Marin Krmpotić: Implementation and Evaluation of Low-Latency Key-Exchange Protocols (co-supervised with David Derler)
Kevin Pretterhofer: Privacy Enhancing Technologies Made Post-Quantum Secure
Christian Gaisl: Privacy-friendly Payment Schemes from Group Signatures (co-supervised with Christian Hanser and Daniel Kales)
Lukas Alber: A Short-Lived Answer to Full Delegation: Applying Time-Bound Identity-Based Signatures to TLS (co-supervised with Stefan More)
Simon Gärtner: Evaluierung und Integration von Post-Quantum-Signaturverfahren auf Embedded-Devices
Sonja Bruckner: A New AKE Protocol for the Application in QKDNs Without Trusted Nodes
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.
Contact Information¶
E-mail: sebastian.ramacher@ait.ac.at or sebastian@ramacher.at.
Keybase.io: sebastinas.