About
SBA Research is a research center for Information Security funded partly by the national initiative for COMET
Competence
Centers for Excellent Technologies. Within a network of more than 70 companies, 15 Austrian and international
universities
and research institutions, and many additional international research partners we jointly work on research
challenges
ranging from organizational to technical security to strengthen Europe’s Cybersecurity capabilities
Decentralized Systems Group
The Decentralized Systems Group at SBA Research focuses on fundamental and applied research in the field of
blockchain
and distributed ledger technologies. Current projects explore,
consensus mechanism,
self-sovereign identities,
and cross-chain interoperability
mechanisms.
To industry partners we offer technical workshops, feasibility studies, project consulting, and contract
research.
A Glance Beyond the Hype
Following the introduction of Bitcoin and the swift rise of cryptocurrencies, blockchain and distributed
ledger technologies have received global attention not least from governments, industry and research institutions.
While cryptocurrencies as distributed, trustless and self-governing systems aim to provide an alternative to traditional fiat
currency structures, the underlying technologies have shown applicability to a wide range of domains beyond
financial services.
As such, we have witnessed first deployments of blockchain-based application prototypes
facilitating,
inter alia, transparent record keeping, auditable supply chain management and machine-to-machine communication
of autonomous (IoT) agents.
However, a closer analysis of the current state of the technical concepts, implementations and tool support
reveals these systems are bleeding edge technology and mainstream adoption is a long way ahead.
Furthermore, there exists no one blockchain to be used as golden hammer for all use cases and problems,
while secure and efficient inter-chain communication has yet to be developed.
Hence, thorough analysis of requirements, applicability and technical feasibility are of vital importance
when deciding upon whether to replace/extend existing systems by/with blockchain-based solutions. Thereby, the core question
is not whether "blockchain" is applicable but which of the existing approaches is most suitable.
Research
Research focus
We conduct fundamental and applied research on the security, privacy, reliability, and performance of
decentralized and distributed systems. Our work spans distributed consensus and digital payments;
blockchain and distributed-ledger technologies; smart contracts and verifiable computation; cryptographic
key management and digital identity; privacy-enhancing technologies; secure group messaging and federation;
decentralized storage; and dependable coordination of autonomous agents.
We combine protocol and systems analysis, empirical measurement, attack research, and the design and
evaluation of practical countermeasures.
Preprints and ePrints
arXiv
Systematization of Knowledge: The Design Space of Digital Payment Systems with Potential for CBDC
Judith Senn, Aljosha Judmayer, Nicholas Stifter, and Rainer Böhme
arXiv:2603.16320, 2026.
ePrint
Analyzing UTXO-Based Blockchain Privacy Threats
Simin Ghesmati, Walid Fdhila, and Edgar Weippl
Cryptology ePrint Archive, Paper 2023/1862, 2023.
ePrint
Agreement with Satoshi – On the Formalization of Nakamoto Consensus
Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, Alexei Zamyatin, and Edgar Weippl
Cryptology ePrint Archive, Paper 2018/400, 2018.
ePrint
Flux: Revisiting Near Blocks for Proof-of-Work Blockchains
Alexei Zamyatin, Nicholas Stifter, Philipp Schindler, Edgar Weippl, and William J. Knottenbelt
Cryptology ePrint Archive, Paper 2018/415, 2018.
Peer-reviewed publications
2026
USENIX
Send and Pretend: Exploiting Transcript Consistency Issues in End-to-End Encrypted Group Chats
Gabriel K. Gegenhuber, Moritz Grefner, Maximilian Günther, Matthäus Wininger, David Schmidt, and Aljosha Judmayer
35th USENIX Security Symposium (USENIX Security '26), 2026.
arXiv
NDSS
Hey there! You are using WhatsApp: Enumerating Three Billion Accounts for Security and Privacy
Gabriel K. Gegenhuber, Philipp É. Frenzel, Maximilian Günther, Johanna Ullrich, and Aljosha Judmayer
Network and Distributed System Security Symposium (NDSS 2026), 2026.
DOI
arXiv
Reuse of Public Keys Across UTXO and Account-Based Cryptocurrencies
Rainer Stütz, Nicholas Stifter, Melitta Dragaschnig, Bernhard Haslhofer, and Aljosha Judmayer
Financial Cryptography and Data Security 2026.
2025
arXiv
Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers
Gabriel K. Gegenhuber, Maximilian Günther, Markus Maier, Aljosha Judmayer, Florian Holzbauer, Philipp É. Frenzel, and Johanna Ullrich
28th International Symposium on Research in Attacks, Intrusions and Defenses (RAID 2025).
Best Paper Award.
USENIX
Prekey Pogo: Investigating Security and Privacy Issues in WhatsApp’s Handshake Mechanism
Gabriel Karl Gegenhuber, Philipp É. Frenzel, Maximilian Günther, and Aljosha Judmayer
19th USENIX WOOT Conference on Offensive Technologies (WOOT '25), pp. 209–227, 2025.
arXiv
DOI
Sicherstellung und Beschlagnahme von Kryptowerten im Strafprozessrecht – Eine Analyse der neuen Rechtslage
Evelyne Putz and Nicholas Stifter
Spektrum des Wirtschaftsrechts, pp. 7–30, 2025.
2024
DOI
Not Your Keys, Not Your Coins? Rechtliche Lücken bei der Sicherstellung von Kryptowerten und Analyse der vorgesehenen Änderungen im Strafprozessrechtsänderungsgesetz 2024
Evelyne Putz, Nicholas Stifter, and Edgar Weippl
Spektrum des Wirtschaftsrechts, pp. 55–82, 2024.
2023
Record
Blockchain-Babel: Herausforderungen bei der Entwicklung präziser Begrifflichkeiten zwischen Recht und Technik im Kontext von Kryptowährungen und Distributed-Ledger-Technologien
Nicholas Stifter, Aljosha Judmayer, Evelyne Putz, Georg Brameshuber, and Edgar R. Weippl
In Handbuch Besteuerung von Kryptowährungen, Facultas, Vienna, 2023.
DOI
User-Perceived Privacy in Blockchain
Simin Ghesmati, Walid Fdhila, and Edgar Weippl
Financial Cryptography and Data Security, FC 2022 International Workshops, LNCS 13412, pp. 164–194, 2023.
Open version
DOI
Estimating (Miner) Extractable Value is Hard, Let’s Go Shopping!
Aljosha Judmayer, Nicholas Stifter, Philipp Schindler, and Edgar Weippl
Financial Cryptography and Data Security, FC 2022 International Workshops, LNCS 13412, pp. 74–92, 2023.
ePrint
2022
DOI
Opportunistic Algorithmic Double-Spending: How I Learned to Stop Worrying and Love the Fork
Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, and Edgar Weippl
Computer Security – ESORICS 2022, LNCS 13554, pp. 46–66, 2022.
ePrint
Open version
Challenges and Opportunities of Blockchain for Auditable Processes in the Healthcare Sector
Walid Fdhila, Nicholas Stifter, and Aljosha Judmayer
Business Process Management: Blockchain, Robotic Process Automation, and Central and Eastern Europe Forum, pp. 68–83, 2022.
DOI
How Much Is the Fork? Fast Probability and Profitability Calculation During Temporary Forks
Aljosha Judmayer, Nicholas Stifter, Philipp Schindler, and Edgar Weippl
Companion Proceedings of the Web Conference 2022, pp. 467–477, 2022.
Record
User Centric Public Blockchain Privacy Threats
Simin Ghesmati, Walid Fdhila, and Edgar Weippl
Workshop on Privacy Threat Modeling (WPTM 2022), 2022.
DOI
SoK: How Private Is Bitcoin? Classification and Evaluation of Bitcoin Privacy Techniques
Simin Ghesmati, Walid Fdhila, and Edgar Weippl
17th International Conference on Availability, Reliability and Security (ARES 2022), Article 5, pp. 1–14, 2022.
Paper
Usability of Cryptocurrency Wallets Providing CoinJoin Transactions
Simin Ghesmati, Walid Fdhila, and Edgar Weippl
Usable Security and Privacy Symposium (USEC 2022), 2022.
2021
Open version
Methods for Decentralized Identities: Evaluation and Insights
Walid Fdhila, Nicholas Stifter, Kristian Kostal, Cihan Saglam, and Markus Sabadello
Business Process Management: Blockchain and Robotic Process Automation Forum, pp. 119–135, 2021.
DOI
Unnecessary Input Heuristics and PayJoin Transactions
Simin Ghesmati, Andreas Kern, Aljosha Judmayer, Nicholas Stifter, and Edgar Weippl
HCI International 2021 – Posters, CCIS 1420, pp. 416–424, 2021.
ePrint
ePrint
RandRunner: Distributed Randomness from Trapdoor VDFs with Strong Uniqueness
Philipp Schindler, Aljosha Judmayer, Markus Hittmeir, Nicholas Stifter, and Edgar Weippl
Network and Distributed System Security Symposium (NDSS 2021), 2021.
DOI
Studying Bitcoin Privacy Attacks and Their Impact on Bitcoin-Based Identity Methods
Simin Ghesmati, Walid Fdhila, and Edgar Weippl
Business Process Management: Blockchain and Robotic Process Automation Forum, LNBIP 428, pp. 85–101, 2021.
ePrint
ePrint
What Is Meant by Permissionless Blockchains?
Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, Andreas Kern, and Walid Fdhila
IEEE Crypto Valley Conference on Blockchain Technology, 2021.
ePrint
Pay to Win: Cheap, Cross-Chain Bribing Attacks on PoW Cryptocurrencies
Aljosha Judmayer, Nicholas Stifter, Alexei Zamyatin, Itay Tsabary, Ittay Eyal, Peter Gazi, Sarah Meiklejohn, and Edgar Weippl
5th Workshop on Trusted Smart Contracts, Financial Cryptography 2021.
ePrint
SoK: Algorithmic Incentive Manipulation Attacks on Permissionless PoW Cryptocurrencies
Aljosha Judmayer, Nicholas Stifter, Alexei Zamyatin, Itay Tsabary, Ittay Eyal, Peter Gazi, Sarah Meiklejohn, and Edgar Weippl
5th Workshop on Trusted Smart Contracts, Financial Cryptography 2021.
2020
ePrint
HydRand: Efficient Continuous Distributed Randomness
Philipp Schindler, Aljosha Judmayer, Nicholas Stifter, and Edgar Weippl
IEEE Symposium on Security and Privacy, 2020.
2019
Paper
A Deep Dive into Bitcoin Mining Pools: An Empirical Analysis of Mining Shares
Matteo Romiti, Aljosha Judmayer, Alexei Zamyatin, and Bernhard Haslhofer
Workshop on the Economics of Information Security (WEIS 2019).
ePrint
XCLAIM: Trustless, Interoperable, Cryptocurrency-Backed Assets
Alexei Zamyatin, Dominik Harz, Joshua Lind, Panayiotis Panayiotou, Arthur Gervais, and William J. Knottenbelt
IEEE Symposium on Security and Privacy, pp. 193–210, 2019.
ePrint
Distributed Key Generation with Ethereum Smart Contracts
Philipp Schindler, Aljosha Judmayer, Nicholas Stifter, and Edgar Weippl
1st Cryptocurrency Implementers' Workshop (CIW '19), Financial Cryptography 2019.
Paper
Echoes of the Past: Recovering Blockchain Metrics from Merged Mining
Nicholas Stifter, Philipp Schindler, Aljosha Judmayer, Alexei Zamyatin, Andreas Kern, and Edgar Weippl
Financial Cryptography and Data Security 2019.
ePrint
Uncle Traps: Harvesting Rewards in a Queue-Based Ethereum Mining Pool
Sebastian Werner, Philipp Pritz, Alexei Zamyatin, and William J. Knottenbelt
12th EAI International Conference on Performance Evaluation Methodologies and Tools (VALUETOOLS 2019).
DOI
Revisiting Practical Byzantine Fault Tolerance Through Blockchain Technologies
Nicholas Stifter, Aljosha Judmayer, and Edgar Weippl
In Security and Quality in Cyber-Physical Systems Engineering, pp. 471–495, 2019.
2018
ePrint
Pitchforks in Cryptocurrencies: Enforcing Rule Changes Through Offensive Forking and Consensus Techniques
Aljosha Judmayer, Nicholas Stifter, Philipp Schindler, and Edgar Weippl
International Workshop on Cryptocurrencies and Blockchain Technology (CBT 2018).
Paper
Proof-of-Blackouts? How Proof-of-Work Cryptocurrencies Could Affect Power Grids
Johanna Ullrich, Nicholas Stifter, Aljosha Judmayer, Adrian Dabrowski, and Edgar Weippl
International Symposium on Research in Attacks, Intrusions, and Defenses (RAID 2018).
DOI
Committing to Quantum Resistance: A Slow Defence for Bitcoin Against a Fast Quantum Computing Attack
Iain Stewart, Dragos Ilie, Alexei Zamyatin, Sam Werner, M. F. Torshizi, and William J. Knottenbelt
Royal Society Open Science 5:180410, 2018.
Paper
A Wild Velvet Fork Appears! Inclusive Blockchain Protocol Changes in Practice
Alexei Zamyatin, Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, Edgar Weippl, and William J. Knottenbelt
5th Workshop on Bitcoin and Blockchain Research, Financial Cryptography 2018.
2017
Paper
Merged Mining: Curse or Cure?
Aljosha Judmayer, Alexei Zamyatin, Nicholas Stifter, Artemios G. Voyiatzis, and Edgar R. Weippl
International Workshop on Cryptocurrencies and Blockchain Technology (CBT 2017).
Paper
Swimming with Fishes and Sharks: Beneath the Surface of Queue-Based Ethereum Mining Pools
Alexei Zamyatin, Katinka Wolter, Sam Werner, Catherine E. A. Mulligan, Peter G. Harrison, and William J. Knottenbelt
25th IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS 2017).
DOI
Blocks and Chains: Introduction to Bitcoin, Cryptocurrencies, and Their Consensus Mechanisms
Aljosha Judmayer, Nicholas Stifter, Katharina Krombholz, and Edgar R. Weippl
Synthesis Lectures on Information Security, Privacy, and Trust, 2017.
2016
DOI
Condensed Cryptographic Currencies Crash Course (C5)
Aljosha Judmayer and Edgar R. Weippl
ACM SIGSAC Conference on Computer and Communications Security, 2016.
Paper
Cryptographic Currencies Crash Course (C4): Tutorial
Aljosha Judmayer and Edgar R. Weippl
25th International Conference on World Wide Web (WWW 2016).
Record
Für bare Münze? NutzerInnenerfahrungen mit Sicherheit und Datenschutz bei Bitcoin
Katharina Krombholz, Aljosha Judmayer, Matthias Gusenbauer, and Edgar R. Weippl
Sicherheit 2016: Sicherheit, Schutz und Zuverlässigkeit.
Paper
The Other Side of the Coin: User Experiences with Bitcoin Security and Privacy
Katharina Krombholz, Aljosha Judmayer, Matthias Gusenbauer, and Edgar R. Weippl
International Conference on Financial Cryptography and Data Security, 2016.
DOI
Dissertations
Thesis
Privacy and Usability Aspects of Public Blockchains
Simin Ghesmati; advisor: Edgar Weippl
Doctoral dissertation, TU Wien, 2024.
DOI
Thesis
Pay to Win: Algorithmic Incentive Manipulation Attacks on Permissionless Cryptocurrencies
Aljosha Judmayer; advisor: Edgar Weippl
Doctoral dissertation, TU Wien, 2023.
DOI
Articles and outreach
Article
Bitcoin – Cryptocurrencies and Alternative Applications
Aljosha Judmayer, Alexei Zamyatin, Nicholas Stifter, and Edgar Weippl
ERCIM News 110, 2017.
Article
A Holistic Approach to Smart Contract Security
Nicholas Stifter, Aljosha Judmayer, and Edgar Weippl
ERCIM News 110, 2017.
Blocks & Chains Bibliography
We also maintain an archive of publications and online resources on cryptocurrencies and distributed-ledger
technologies in the
Blocks & Chains Bibliography.