Up to Research, Theory group at Nada, KTH.
Cryptography
Researchers
Students
Theoretical cryptography aims at finding mathematically elegant
definitions and constructions. For many applications much more
efficient and simpler constructions can be found by using concrete
assumptions and non-standard definitions of subprotocols and
primitives. Even if it does not give any immediate theoretical
insights it is important to study these relaxed notions.
Practical computer security is to a large extent based on experience
and practitioners ignore parts of the theoretical literature to find
more efficient constructions. This is often not really necessary, as a
more careful study allows provably secure and efficient constructions
that can be implemented in the real world.
In the project we try to bridge some of this gap by: investigating
practically oriented definitions and primitives, finding provably
secure and practical constructions, and implementing parts of these to
illustrate their use and to better understand them.
An important application of cryptographic protocols is electronic
voting and much of our research targets problems in this area.
Publications of the Group
- A Mix-Net From Any CCA2 Secure Cryptosystem
- Shahram Khazaei, Tal Moran, and Douglas Wikström.
- Submitted for publication.
- Cryptanalysis of a universally verifiable efficient re-encryption mixnet
- Shahram Khazaei, Björn Terelius, and Douglas Wikström.
- Cryptology ePrint Archive, Report 2012/100, 2012. Submitted for publication.
- Randomized partial checking revisited
- Shahram Khazaei and Douglas Wikström.
- Cryptology ePrint Archive, Report 2012/063, 2012. Submitted for publication.
- Efficiency limitations of Sigma-protocols for group homomorphisms revisited
- Björn Terelius and Douglas Wikström.
- Submitted for publication.
- Wombat: An implementation and field testing of dual paper-cryptographic election system
- Jonathan Ben-Nun, Niko Farhi, Morgan Llewellyn, Ben Riva, Alon Rosen, Amnon Ta-Shma, and Douglas Wikström
- To appear at EVOTE 2012
- Parallel repetition of computationally sound protocols revisited
- Krzysztof Pietrzak and Douglas Wikström
- J. Cryptology, 25(1):116-135, (2012
- On the composition of public-coin zero-knowledge protocols
- Rafael Pass, Wei-Lung Dustin Tseng, and Douglas Wikström
- SIAM J. Comput., 40(6):1529-1553, (2011
- An efficient parallel repetition theorem
- Johan Håstad, Rafael Pass, Douglas Wikström, and Krzystof Pietrzak
- TCC 2010: 1-1
- Proofs of restricted shuffles
- Björn Terelius and Douglas Wikström
- AFRICACRYPT 2010: 100-11
- Group message authentication
- Bartosz Przydatek and Douglas Wikström
- SCN 2010: 399-41
- Practical private information aggregation in large networks
- Gunnar Kreitz, Mads Dam, and Douglas Wikström
- NORDSEC 2010: 231-243, 2010.
- On the composition of public-coin zero-knowledge protocols
- Rafael Pass, Wei-Lung Dustin Tseng, and Douglas Wikström
- CRYPTO 2009: 160-17
- A commitment-consistent proof of a shuffle
- Douglas Wikström
- ACISP 2009: 407-42
- Simplified submission of inputs to protocols
- Douglas Wikström
- SCN 2008: 293-30
- Practical Construction and Analysis of Pseudo-Randomness Primitives
- Johan Håstad, Mats Näslund
- J. Cryptology 21(1): 1-26 (2008)
- The Security of the IAPM and IACBC Modes
- Johan Håstad
- J. Cryptology 20(2): 153-163 (2007)
- Offline/Online Mixing
- Ben Adida, Douglas Wikström
- ICALP 2007, pp. 484-495
- Designated Confirmer Signatures Revisited
- Douglas Wikström
- TCC 2007: 342-361
- How to Shuffle in Public
- Ben Adida, Douglas Wikström
- TCC 2007: 555-574
- Parallel Repetition of Computationally Sound Protocols Revisited
- Krzysztof Pietrzak, Douglas Wikström
- TCC 2007: 86-102
- An Adaptively Secure Mix-Net Without Erasures
- Douglas Wikström, Jens Groth
- ICALP (2) 2006: 276-287
- A Sender Verifiable Mix-Net and a New Proof of a Shuffle
- Douglas Wikström
- ASIACRYPT 2005: 273-292
- Hierarchical Group Signatures
- Mårten Trolin, Douglas Wikström
- ICALP 2005: 446-458
- A Universally Composable Scheme for Electronic Cash
- Mårten Trolin
- INDOCRYPT 2005: 347-360
- Randomness Extraction and Key Derivation Using the CBC, Cascade and HMAC Modes
- Yevgeniy Dodis, Rosario Gennaro, Johan Håstad, Hugo Krawczyk, Tal Rabin
- CRYPTO 2004: 494-510
- The security of all RSA and discrete log bits
- Johan Håstad, Mats Näslund
- J. ACM 51(2): 187-230 (2004)
- Universally Composable DKG with Linear Number of Exponentiations
- Douglas Wikström
- SCN 2004: 263-277
- A Universally Composable Mix-Net
- Douglas Wikström
- TCC 2004: 317-335
- Lattices with Many Cycles Are Dense
- Mårten Trolin
- STACS 2004: 370-381
- Universally Composable Protocols with Relaxed Set-Up Assumptions
- Boaz Barak, Ran Canetti, Jesper Buus Nielsen, Rafael Pass
- FOCS 2004: 186-195
- Bounded-concurrent secure multi-party computation with a dishonest majority
- Rafael Pass
- STOC 2004: 232-241
- On the Possibility of One-Message Weak Zero-Knowledge
- Boaz Barak, Rafael Pass
- TCC 2004: 121-132
- Lattices with Many Cycles Are Dense
- Mårten Trolin
- Electronic Colloquium on Computational Complexity (ECCC)(113): (2004)
- Five Practical Attacks for 'Optimistic Mixing for Exit-Polls'
- Douglas Wikström
- Selected Areas in Cryptography 2003: 160-175
- Nearly One-Sided Tests and the Goldreich?Levin Predicate
- Gustav Hast
- J. Cryptology 17(3): 209-229 (2004)
- Nearly One-Sided Tests and the Goldreich-Levin Predicate
- Gustav Hast
- EUROCRYPT 2003: 195-210
- On Deniability in the Common Reference String and Random Oracle Model
- Rafael Pass
- CRYPTO 2003: 316-337
- Simulation in Quasi-Polynomial Time, and Its Application to Protocol Composition
- Rafael Pass
- EUROCRYPT 2003: 160-176
- Bounded-Concurrent Secure Two-Party Computation in a Constant Number of Rounds
- Rafael Pass, Alon Rosen
- FOCS 2003: 404-
- A Note on the Malleability of the El Gamal Cryptosystem
- Douglas Wikström
- INDOCRYPT 2002: 176-184
- The Security of a Mix-Center Based on a Semantically Secure Cryptosystem
- Douglas Wikström
- INDOCRYPT 2002: 368-381
- Practical Construction and Analysis of Pseudo-Randomness Primitives
- Johan Håstad, Mats Näslund
- ASIACRYPT 2001: 442-459
- The Shortest Vector Problem in Lattices with Many Cycles
- Mårten Trolin
- CaLC 2001: 194-205
- On the complexity of interactive proof with bounded communication
- O. Goldreich, J. Håstad,
- Information processing letters, Vol.~67 (4), 1998, pp 205-214.
- postscript
-
- A Pseudorandom Generator from any one-way function
- J. Håstad, R. Imagliazzo, L. Levin, and M. Luby
- SIAM Journal on Computing, Vol 28, 1999, pp 1364-1396.
- postscript
- The Security of Individual RSA Bits
- J. Håstad and M. Näslund
- Proceedings, FOCS '98, pp 510-519, IEEE.
- A more complete version of this is contained in Mats Näslund's
thesis found below.
- Bit Extraction, Hard-Core Predicates, and the Bit Security of RSA
- M. Näslund
- Ph.D. Thesis, Nada, October, 1998
- PDF.
- The Complexity of Computing Hard Core Predicates
- M. Goldmann and M. Näslund
- Proceedings, CRYPT0 '97. LNCS 1294, pp 1-15, Springer Verlag.
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- Pseudo-Random Generators under Uniform Assumptions
- J. Håstad
- Proceedings, 22nd STOC, 1990, pp 395-404.
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- The Discrete Logarithm Modulo a Composite Hides O(n) Bits
- J. Håstad, A. W. Schrift, and A. Shamir
- JCSS 47 1993, pp. 376-403
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- Universal Hash Functions & Hard Core Bits
- M. Näslund
- Proceedings, EUROCRYPT '95, LNCS 921, pp 356-366, Springer Verlag
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- All Bits in ax+b mod p are Hard
- M. Näslund
- Proceedings, CRYPT0 '96. LNCS 1109, pp 114-128, Springer Verlag.
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Previous Members of the Group
- Mats Näslund (now at Ericsson)
- Gustav Hast (now at Exportkredit)
- Mårten Trolin (now at Ernst and Young)
- Rafael Pass (now at Cornell University)
Up to Research, Theory group at Nada, KTH.
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