Krzysztof Pietrzak (Professor) pietrzak@ist.ac.atBenedikt Auerbach (Postdoc)
Georgia (Zeta) Avarikioti (Postdoc)
Suvradip Chakraborty (Postdoc)
Michael Walter (Postdoc)
Karen Klein (PhD. student)
Guillermo Perez (PhD. student)
Michelle Yeo (PhD. student)
Mirza Baig (PhD. student)
Charlotte Hoffmann (PhD. student)
Chethan Kamath, Michelle Yeo, Michael Walter, Guillermo Perez, Krzysztof Pietrzak, Miguel Cueto (ISTern), Ahmadreza Rahimi (visiting), Margarita Capretto (ISTern), Karen Klein
The cryptography group at IST Austria works on theoretical and practical aspect of cryptography.
Several of our current topics involve graph-pebbling as described here, here you can try to consruct a hard to pebble graph.Some of our current research interest are
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Sustainable Cryptocurrencies. Bitcoin is the first successful digital currency. Its popularity comes from the fact that it is decentralised, so no central authority controls it. To achieve security despite decentralisation a huge amount of computing power is constantly wasted towards generating Proofs of Work, this is economically and ecologically problematic. We work on more "sustainable" cryptocurrencies.
Towards this goal we introduced the concept of "Proofs of Space" [DFKP'15],[ACK+'16],[Pie'19] as a replacement for Proofs of Work. An academic proposal using proofs of space is the Spacemint cryptocurrency [PPK+'15]. We are involved with the Chia network which will combine proofs of space with verifiable delay functions (VDF).
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Memory-hard Functions (MHF) are functions which require a large amount of memory to be evaluated. Despite having found many applications, until recently there were no meaningful security proofs MHFs at all. MHFs come in two flavours, data-dependent and data-independent. In [ACPRT'17] (Best Paper Award at Eurocrypt'17) we show that Scrypt is an "optimal" data depentend MHF. In [ABP'16] we show how "depth robust" graphs give rise to data independent MHFs with optimal parameters. In a series of papers [AB'16a],[AB'16b],[AGK+'16b] we break most of the proposals of data-independent MHFs.
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Crypto for light-weight devices. We work towards provably secure cryptographic schemes for light-weight devices such as RFID tags, which are too constrained to run existing cryptographic schemes. In [KPC+'11] (Best Paper Award at Eurocrypt'11) and [HKL+'12] we construct extremely efficient and provably secure authentiaction schemes based on the the (ring) LPN problems. In [JKPT'12],[BKLP'15] we give commitments with effecient zero-knowledge proofs from the same assumption.
- Symmetric Cryptography. We develop new tools to construct and analyze symmetric (aka secret key) primitives. One focus lies is determening the exact security of popular schemes. We gave such tight bounds for HMAC [GPR'14] (and variants [GPT'15]), PMAC [GPR'17] and CBC [GPT'15].
Adaptively Secure Proxy Re-encryption Public Key Cryptography (PKC) 2019 [full version]
Reversible Proofs of Sequential Work Eurocrypt 2019 [full version]
Finding a Nash Equilibrium is No Easier than Breaking Fiat-Shamir STOC 2019 [full version]
Sampling the Integers with Low Relative Error AFRICACRYPT 2019 [full version]
Simple Verifiable Delay Functions Innovations in Theoretical Computer Science (ITCS) 2019 [full version]
Proofs of Catalytic Space Innovations in Theoretical Computer Science (ITCS) 2019 [full version]
Non-Malleable Codes Journal of the ACM, Volume 65 Issue 4, August 2018 [article][full version]
On the Memory-Hardness of Data-Independent Password-Hashing Functions AsiaCCS 2018 [full version]
Simple Proofs of Sequential Work (Best Paper Award) Eurocrypt 2018 [full version]
Sustained Space Complexity Eurocrypt 2018 [full version]
On the Bit Security of Cryptographic Primitives Eurocrypt 2018 [full version]
Renyi Entropy Estimation Revisited Approx-Random 2017 [proceedings] [full version]
On the Complexity of Breaking Pseudoentropy TAMC 2017 [proceedings] [full version]
Practical Graphs for Optimal Side-Channel Resistant Memory-Hard Functions ACM CCS 2017 [proceedings] [full version]
Beyond Hellman's Time-Memory Trade-Offs with Applications to Proofs of Space Asiacrypt 2017 [full version]
Non-Uniform Attacks Against Pseudoentropy ICALP 2017 [proceedings] [full version]
Position-Based Cryptography and Multiparty Communication Complexity TCC 2017 [proceedings] [full version]
Efficient Authentication from Hard Learning Problems Journal of Cryptography 2017 [article]
Be Adaptive, Avoid Overcommitting Crypto 2017 [proceedings] [full version]
Depth-Robust Graphs and Their Cumulative Memory Complexity Eurocrypt 2017 [proceedings] [full version]
Scrypt is Maximally Memory-Hard (Best Paper Award) Eurocrypt 2017 [proceedings] [full version]
The Exact Security of PMAC ToSC 2017, Volume 1, and FSE 2017 [article] [full version]
Towards Practical Attacks on Argon2i and Balloon Hashing Euro S&P 2017 [proceedings] [full version]
Cumulative Space in Black-White Pebbling and Resolution ITCS 2017
Key Derivation for Squared-Friendly Applications: Lower Bounds STACS 2017 [proceedings] [full version]
Pseudoentropy: Lower-Bounds for Chain Rules and Transformations TCC (B1) 2016 [proceedings] [full version]
Simulating Auxiliary Inputs, Revisited TCC (B1) 2016 [proceedings] [full version]
A counterexample to the chain rule for conditional HILL entropy Computational Complexity 2016 [article] [full version]
Standard Security Does Imply Security Against Selective Opening for Markov Distributions TCC (A1) 2016 [proceedings] [full version]
Practical Round-Optimal Blind Signatures in the Standard Model from Weaker Assumptions SCN 2016 [proceedings] [full version]
A Closer Look at Multiple-Forking: Leveraging (In)dependence for a Tighter Bound Algorithmica 2016, Volume 74 [full version]
On the Complexity of Scrypt and Proofs of Space in the Parallel Random Oracle Model Eurocrypt 2016 [full version]
Efficiently Computing Data-Independent Memory-Hard Functions CRYPTO 2016 [full version]
Provably Robust Sponge-Based PRNGs and KDFs Advances in Cryptology -- Eurocrypt 2016, Lecture Notes in Computer Science, Springer-Verlag, 2016 [proceedings] [full version]
Constrained PRFs for Unbounded Inputs CT-RSA 2016 [proceedings] [full version]
Constrained PRFs for Unbounded Inputs with Short Keys ACNS 2016 [proceedings] [full version]
Offline Witness Encryption ACNS 2016 [proceedings] [full version]
some older publicationsHamza Abusalah (PhD student, graduated 2018)
Joel Alwen (Postdoc) - now at Wickr
Maciej Skorski (Postdoc)
Peter Gazi (Postdoc) - now at IOHK
Georg Fuchsbauer (Postdoc) - now at ENS Paris
Michal Rybar (PhD. student, graduated 2017)
Stephan Krenn (Postdoc) - now at Austrian Institute of Technology
Miguel Cueto, University of Oviedo/Spain, (ISTern, Summer 2019)
Arka Rai Choudhuri , John Hopkins, (graduate summer student, 2018)
Samarth Tiwari , New York University (ISTern, Summer 2018)
Sasha Lapiga , Taras Shevchenko National University of Kyiv (ISTern, Summer 2018)
Anastasia Kucherenko , Taras Shevchenko National University of Kyiv (ISTern, Summer 2017)
Mukesh Pareek , IIT Bombay (ISTern, Summer 2017)
Hana Dlouha , CTU in Prague (ISTern, Summer 2017)
Teresa Steiner, TU Wien (student intern, 2016)
Danylo Khilko, Taras Shevchenko National University of Kyiv (ISTern, 2016) Zahra Jafargholi, UCLA (graduate summer student, 2014) Maciej Skorski, University of Warsaw (graduate summer student, 2012/13/14/15) Sophie Stevens, Bristol (ISTernship, 2014) Kristian Tokmakov, Oxford (ISTernship, 2014) Alexander Golovnev, NYU (graduate summer student, 2014) Momchil Konstantinov, Oxford (ISTernship, 2013) Vanishree Rao, UCLA (graduate summer student, 2013) Akshay Wadia, UCLA (graduate summer student, 2012) Aris Tentes, NYU (graduate summer student, 2011)