Ahto Buldas


Co-Founder, GuardTime

Professor, Tallinn University of Technology

e-mail: ahto.buldas@ttu.ee

Curriculum Vitae:

(in english) , (in estonian)

Selected Publications

  1. Ahto Buldas. Congruence lattice of a graph. Proc. Estonian Acad. Sci. Phys. Math., 1997, 46, 3, 155-170.
  2. Ahto Buldas and Jüri Põldre. A VLSI implementation of RSA and IDEA encryption engine. In NORCHIP'97, Tallinn 1997.
  3. Ahto Buldas, Peeter Laud, Helger Lipmaa, Jan Villemson, "Ajatempli protokollid, turvavajadused ja tehnilised nõuded," Technical Report DO-LU-X-22-1297, Cybernetica, 1997, 46 pages ["Timestamp protocols, security needs and technical requirements". Funded by Estonian Informatics Centre]
  4. Ahto Buldas. Graphs and lattice varieties. Proc. Estonian Acad. Sci. Phys. Math., 1998, 47, 2, 100-109.
  5. Ahto Buldas, Peeter Laud, Helger Lipmaa and Jan Villemson. Time-Stamping with binary linking schemes. In Advances in Cryptology - CRYPTO'98, LNCS 1462, 486-501. Springer-Verlag, 1998. .ps, .pdf, 10.1007/BFb0055749
  6. Ahto Buldas and Peeter Laud. New linking schemes for digital time-stamping. In Proceedings of The 1st International Conference on Information Security and Cryptology - ICISC'98, 3-14, Seoul, Korea, 1998. .ps, .pdf,
  7. Ahto Buldas, Helger Lipmaa and Berry Schoenmakers. Optimally efficient accountable time-stamping. In Public Key Cryptography - PKC'2000, Melbourne, Australia. LNCS 1751, 293-305. Springer-Verlag, 2000. .ps, .pdf, 10.1007/978-3-540-46588-1_20
  8. Ahto Buldas, Meelis Roos, Valdo Praust and Jan Willemson. On long-term validation of E-documents. Baltic IT-Review, 2 (17): 53-56, 2000.
  9. Ahto Buldas, Peeter Laud and Helger Lipmaa. Accountable Certificate Management using undeniable attestations. In The 7th ACM Conference on Computer and Communication Security - CCS'00, Athens, Greece. Nov. 1-4, 2000. .ps, .pdf, 10.1145/352600.352604
  10. Arne Ansper, Ahto Buldas, Meelis Roos and Jan Willemson. Efficient long-term validation of digital signatures. In Public Key Cryptography - PKC'2001, Cheju Island, Korea. Feb. 13-15, 2001. LNCS 1992, 402-415. Springer-Verlag, 2001. .ps, .pdf, 10.1007/3-540-44586-2_29
  11. Arne Ansper, Ahto Buldas, Märt Saarepera and Jan Willemson. Improving the availability of time-stamping services. In The 6th Australasian Conference on Information Security and Privacy - ACISP'2001, Sydney, Australia, July 2-4, 2001. LNCS 2119, 360-375. Springer-Verlag, 2001. .ps, .pdf, 10.1007/3-540-47719-5_29
  12. Ahto Buldas, Peeter Laud, Helger Lipmaa. Eliminating counterevidence with applications to accountable certificate management. Journal of Computer Security, v. 10, n. 3, pp. 273-296, 2002. .pdf
  13. Ahto Buldas, Meelis Roos, Jan Willemson. Undeniable replies for database queries. In H.-M. Haav, A.Kalja, eds., Proc. of the 5th International Baltic Conference On Databases and Information Systems -- Baltic DB\&IS 2002, v.2, pp.215-226. Institute of Cybernetics, Tallinn, 2002. CiteSeerX
  14. Ahto Buldas, Märt Saarepera. Electronic signature system with small number of private keys. In 2nd Annual PKI Research Workshop, pp.96-108. NIST Gaithersburg MD, USA. April 28-29, 2003. .pdf
  15. Arne Ansper, Ahto Buldas, Margus Freudenthal, Jan Willemson. Scalable and Efficient PKI for Inter-Organizational Communication. Annual Computer Security Applications Conference -- ACSAC'2003. .pdf, 10.1109/CSAC.2003.1254335
  16. Ahto Buldas and Märt Saarepera. On provably secure time-stamping schemes. In ASIACRYPT 2004, LNCS 3329, pp. 500--514. 2004. .ps, .pdf 10.1007/978-3-540-30539-2_35
  17. Ahto Buldas, Peeter Laud, Märt Saarepera, Jan Willemson. Universally composable time-stamping schemes with audit. In Information Security Conference -- ISC 2005, LNCS 3650, pp.359--373. 2005. 10.1007/11556992_26
  18. Ahto Buldas, Sven Laur. Do broken hash functions affect the security of time-stamping schemes? In 4th International Conference on Applied Cryptography and Network Security -- ACNS'06, LNCS 3989, pp. 50-65, 2006. 10.1007/11767480_4
  19. Ahto Buldas, Peeter Laud, Jaan Priisalu, Märt Saarepera, and Jan Willemson. Rational Choice of Security Measures via Multi-Parameter Attack Trees. In Critical Information Infrasturctures Security First International Workshop -- CRITIS 2006, LNCS 4347, pp. 235-248, 2006. 10.1007/11962977_19
  20. Ahto Buldas, Sven Laur. Knowledge-binding commitments with applications in time-stamping. In The International Conference on Theory and Practice of Public-Key Cryptography (PKC 2007). Beijin, China, April 16-20, 2007. LNCS 4450, pp. 150-165, 2007. 10.1007/978-3-540-71677-8_11
  21. Ahto Buldas, Triinu Mägi. Practical security analysis of e-voting systems. In the Second International Workshop on Security (IWSEC) 2007. Nara, Japan, October 29-31, 2007. LNCS 4752, pp.320-335, 2007. 10.1007/978-3-540-75651-4_22
  22. Ahto Buldas, Aivo Jürgenson. Does secure time-stamping imply collision-free hash functions? In the 1st International Conference on Provable Security (ProvSec) 2007. Wollongong, Australia, October 31-November 2, 2007. LNCS 4784, pp.138-150, 2007. 10.1007/978-3-540-75670-5_9
  23. Ahto Buldas, Margus Niitsoo. Can we construct unbounded time-stamping schemes from collision-free hash functions? In the 2nd International Conference on Provable Security (ProvSec) 2008. Shanghai, China, October 30-November 1, 2008. LNCS 5324, pp.254-267, 2008. 10.1007/978-3-540-88733-1_18
  24. Ahto Buldas, Aivo Jürgenson, Margus Niitsoo. Efficiency bounds for adversary constructions in black-box reductions. In C. Boyd and J. Gonz.alez Nieto (Eds.): ACISP 2009, LNCS 5594, pp.264-275, 2009. 10.1007/978-3-642-02620-1_19
  25. Ahto Buldas, Sven Laur, Margus Niitsoo. Oracle separation in the non-uniform model. In J.Pieprzyk and F.Zhang (Eds.): the 3rd International Conference on Provable Security (ProvSec) 2009, November 11-13, 2009, Guangzhou, China. LNCS 5848, pp. 230-244, 2009. 10.1007/978-3-642-04642-1_19
  26. Ahto Buldas, Margus Niitsoo. Optimally tight security proofs for hash-then-publish time-stamping. In: Steinfeld, R., Hawkes, P. (eds.): ACISP 2010. LNCS 6168, pp.318-335, 2010. 10.1007/978-3-642-14081-5_20
  27. Ahto Buldas, Roman Stepanenko. Upper bounds for adversaries' utility in attack trees. In: J. Grossklags and J. Walrand (Eds.): GameSec 2012, LNCS 7638, pp. 98-117, 2012. 10.1007/978-3-642-34266-0_6 (.pdf)
  28. Ahto Buldas, Margus Niitsoo. Black-box separations and their adaptability to the non-uniform model. In: C. Boyd and L. Simpson (Eds.): ACISP 2013, LNCS 7959, pp. 152-167, 2013. 10.1007/978-3-642-39059-3_11
  29. Ahto Buldas, Risto Laanoja. Security proofs for hash tree time-stamping using hash functions with small output size. In: C. Boyd and L. Simpson (Eds.): ACISP 2013, LNCS 7959, pp. 235-250, 2013. 10.107/978-3-642-39059-3_16
  30. Ahto Buldas, Andres Kroonmaa, Risto Laanoja. Keyless signatures infrastructure: How to build global distributed hash-trees. In: H. Riis Nielson and D. Gollmann (Eds.): NordSec 2013, LNCS 8208, pp. 313-320. Springer, Heidelberg (2013) 10.1007/978-3-642-41488-6_21
  31. Arne Ansper, Ahto Buldas, Margus Freudenthal, Jan Willemson. High-performance qualified digital signatures for X-Road. In: H. Riis Nielson and D. Gollmann (Eds.): NordSec 2013, LNCS 8208, pp. 123-138. Springer Heidelberg (2013) 10.1007/978-3-642-41488-6_9
  32. Arne Ansper, Ahto Buldas, Margus Freudenthal, Jan Willemson. Protecting a federated database infrastructure against denial-of-service attacks. In: E. Luiijf and P. Hartel (Eds.): CRITIS 2013, LNCS 8328, pp. 26-37, 2013. 10.1007/978-3-319-03964-0_3
  33. Ahto Buldas, Aleksandr Lenin. New efficient utility upper bounds for the fully adaptive model of attack trees. In: S.K. Das, C. Nita-Rotaru, and M.Kantarcioglu (Eds.): GameSec 2013, LNCS 8252, pp. 192-205. Springer International Publishing Switzerland (2013) 10.1007/978-3-319-02786-9_12
  34. Ahto Buldas, Risto Laanoja, Peeter Laud, Ahto Truu. Bounded pre-image awareness and the security of hash-tree keyless signatures. In: S.S.M. Chow, J.K. Liu, L.C.K. Hui, and S.M. Yiu (Eds.): Provsec 2014, LNCS 8782, pp. 130-145, 2014. 10.1007/978-3-319-12475-9_10
  35. Ahto Buldas, Aleksandr Lenin. Limiting adversarial budget in quantitative security analysis. In: R. Poovendran and W. Saad (Eds.): GameSec 2014, LNCS 8840, pp. 153-172, 2014. 10.1007/978-3-319-12601-2_9
  36. Ahto Buldas, Ahto Truu, Risto Laanoja, Rainer Gerhards. Efficient record-level keyless signatures for audit logs. In: K. Bernsmed and S. Fisher-Hübner (Eds.): NordSec 2014, LNCS 8788, pp. 149-164, 2014. 10.1007/978-3-319-11599-3_9
  37. Ahto Buldas, Risto Laanoja, Ahto Truu. Keyless signature infrastructure and PKI: hash-tree signatures in pre- and post-quantum world. International Journal of Services Technology and Management (IJSTM), Vol. 23, No. 1/2, 2017. 10.1504/IJSTM.2017.10002708"
  38. Ahto Buldas, Märt Saarepera. Are the current system engineering practices sufficient to meet cyber crime? In: Tryfonas T. (Ed.): HAS 2017. LNCS 10292, pp. 451-463, 2017. 10/007/978-3-319-58460-7_31
  39. Ahto Buldas, Matthias Geihs, Johannes Buchmann. Long-term secure commitments via extractable-binding commitments. In: Pieprzyk, J., Suriadi, S. (Eds.): ACISP 2017, LNCS 10343, pp. 65-81, 2017. 10.1007/978-3-319-60055-0_4
  40. Ahto Buldas, Aivo Kalu, Peeter Laud, and Mart Oruaas: Server-supported RSA signatures for mobile devices. Foley, S.N., Gollmann, D., Snekkenes, E. (Eds.): ESORICS 2017, Part I, LNCS 10492, pp. 1–19, 2017. 10.1007/978-3-319-66402-6_19
  41. Ahto Buldas, Aleksandr Lenin, Jan Willemson, and Anton Charnamord: Simple infeasibility certificates for attack trees. In: S. Obana, K. Chida (Eds.): IWSEC 2017, LNCS 10418, pp. 39-55, 2017. 10.1007/978-3-319-64200-0_3
  42. Ahto Buldas, Matthias Geihs, Johannes Buchmann: Long-term secure time-stamping using preimage-aware hash functions. In: Okamoto, T., Yu, Y. (Eds.): ProvSec 2017. The 11th International Conference on Provable Security, October 23 - 25, 2017, Xi'an, China (to appear) Extended version: Cryptology ePrint Archive 2017/754: (.pdf)

Lecture Notes

IDS0010 Sissejuhatus andmeturbesse

ITX8110 Introduction to Combinatorics and Cryptography

Complexity Theory (Univ. of Tartu)

Combinatorics (Univ. of Tartu)

Sissejuhatus krüptograafiasse

Hulgateooria (Set Theory), Spring 1994 (.pdf)

Sissejuhatus Galois' teooriasse (Introduction to the Galois' Theory, 1993, seminar notes)

Students' Seminar Slides

Seminar for Cyber Defence Students, Autumn 2011

Seminar for Cyber Defence Students, Autumn 2012

Selected Popular Math Stories

All in Estonian

Arvud ja mängud (ettekantud TPedI seminaris,1995)

Goodsteini teoreemist (avaldatud A&A)

Graafid ja järjestused (avaldatud A&A)

Sissejuhatus matroidide teooriasse (avaldatud A&A)

Graafi modulaardekompositsioon (Leo Võhandu seminari ettekanne)

Mis on p-aadilised arvud? (avaldatud A&A)

Algoritmid ja diagonaalsed tõestused (avaldatud A&A)