Byzantine Agreement Using Partial Authentication

  • Piyush Bansal
  • Prasant Gopal
  • Anuj Gupta
  • Kannan Srinathan
  • Pranav Kumar Vasishta
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6950)


Three decades ago, Pease et al. introduced the problem of Byzantine Agreement [PSL 80] where nodes need to maintain a consistent view of the world in spite of the challenge posed by Byzantine faults. Subsequently, it is well known that Byzantine agreement over a completely connected synchronous network of n nodes tolerating up to t faults is (efficiently) possible if and only if t < n/3. Pease et al. further empowered the nodes with the ability to authenticate themselves and their messages and proved that agreement in this new model (popularly known as authenticated Byzantine agreement (ABA)) is possible if and only if t < n. (which is a huge improvement over the bound of t < n/3 in the absence of authentication for the same functionality).

To understand the utility, potential and limitations of using authentication in distributed protocols for agreement, Gupta et al. [GGBS10] studied ABA in new light. They generalize the existing models and thus, attempt to give a unified theory of agreements over the authenticated and non-authenticated domains. In this paper we extend their results to synchronous (undirected) networks and give a complete characterization of agreement protocols.

As a corollary, we show that agreement can be strictly easier than all-pair point-to-point communication. It is well known that in a synchronous network over n nodes of which up to any t are corrupted by a Byzantine adversary, BA is possible only if all pair point-to-point reliable communication is possible [Dol82, DDWY93]. Thus, a folklore in the area is that maintaining global consistency (agreement) is at least as hard as the problem of all pair point-to-point communication. Equivalently, it is widely believed that protocols for BA over incomplete networks exist only if it is possible to simulate an overlay-ed complete network. Surprisingly, we show that the folklore is not always true. Thus, it seems that agreement protocols may be more fundamental to distributed computing than reliable communication.


Byzantine agreement reliable communication general networks authentication 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. [AFM99]
    Altmann, B., Fitzi, M., Maurer, U.M.: Byzantine agreement secure against general adversaries in the dual failure model. In: Jayanti, P. (ed.) DISC 1999. LNCS, vol. 1693, pp. 123–139. Springer, Heidelberg (1999)CrossRefGoogle Scholar
  2. [BGG+]
    Bansal, P., Gopal, P., Gupta, A., Srinathan, K., Vasishta, P.K.: Byzantine agreement using partial authentication. Technical report,
  3. [Bor95]
    Borcherding, M.: On the number of authenticated rounds in byzantine agreement. In: Helary, J.-M., Raynal, M. (eds.) WDAG 1995. LNCS, vol. 972, pp. 230–241. Springer, Heidelberg (1995)CrossRefGoogle Scholar
  4. [Bor96a]
    Borcherding, M.: Levels of authentication in distributed agreement. In: Babaoğlu, Ö., Marzullo, K. (eds.) WDAG 1996. LNCS, vol. 1151, pp. 40–55. Springer, Heidelberg (1996)CrossRefGoogle Scholar
  5. [Bor96b]
    Borcherding, M.: Partially authenticated algorithms for byzantine agreement. In: ISCA: Proceedings of the 9th International Conference on Parallel and Distributed Computing Systems, pp. 8–11 (1996)Google Scholar
  6. [DDS87]
    Dolev, D., Dwork, C., Stockmeyer, L.: On the minimal synchronism needed for distributed consensus. J. ACM 34(1), 77–97 (1987)MathSciNetCrossRefzbMATHGoogle Scholar
  7. [DDWY93]
    Dolev, D., Dwork, C., Waarts, O., Yung, M.: Perfectly Secure Message Transmission. Journal of the Association for Computing Machinery (JACM) 40(1), 17–47 (1993)MathSciNetCrossRefzbMATHGoogle Scholar
  8. [Dol82]
    Dolev, D.: The Byzantine Generals Strike Again. Journal of Algorithms 3(1), 14–30 (1982)MathSciNetCrossRefzbMATHGoogle Scholar
  9. [DS83]
    Dolev, D., Strong, H.R.: Authenticated algorithms for byzantine agreement. SIAM Journal on Computing 12(4), 656–666 (1983)MathSciNetCrossRefzbMATHGoogle Scholar
  10. [FLP85]
    Fischer, M.J., Lynch, N.A., Paterson, M.S.: Impossibility of distributed consensus with one faulty process. J. ACM 32(2), 374–382 (1985)MathSciNetCrossRefzbMATHGoogle Scholar
  11. [FM98]
    Fitzi, M., Maurer, U.M.: Efficient byzantine agreement secure against general adversaries. In: Kutten, S. (ed.) DISC 1998. LNCS, vol. 1499, pp. 134–148. Springer, Heidelberg (1998)CrossRefGoogle Scholar
  12. [GGBS10]
    Gupta, A., Gopal, P., Bansal, P., Srinathan, K.: Authenticated Byzantine Generals in Dual Failure Model. In: Kant, K., Pemmaraju, S.V., Sivalingam, K.M., Wu, J. (eds.) ICDCN 2010. LNCS, vol. 5935, pp. 79–91. Springer, Heidelberg (2010)CrossRefGoogle Scholar
  13. [GLR95]
    Gong, L., Lincoln, P., Rushby, J.: Byzantine agreement with authentication: Observations and applications in tolerating hybrid and link faults (1995)Google Scholar
  14. [HM97]
    Hirt, M., Maurer, U.: Complete Characterization of Adversaries Tolerable in Secure Multi-party Computation. In: Proceedings of the 16th Symposium on Principles of Distributed Computing (PODC), August 1997, pp. 25–34. ACM Press, New York (1997)Google Scholar
  15. [HM00]
    Hirt, M., Maurer, U.M.: Player simulation and general adversary structures in perfect multiparty computation. J. Cryptology 13(1), 31–60 (2000)MathSciNetCrossRefzbMATHGoogle Scholar
  16. [LSP82]
    Lamport, L., Shostak, R., Pease, M.: The byzantine generals problem. ACM Trans. Program. Lang. Syst. 4(3), 382–401 (1982)CrossRefzbMATHGoogle Scholar
  17. [Lyn96]
    Lynch, N.: Distributed Algorithms. Morgan Kaufmann, San Mateo (1996)zbMATHGoogle Scholar
  18. [PSL80]
    Pease, M., Shostak, R., Lamport, L.: Reaching agreement in the presence of faults. J. ACM 27(2), 228–234 (1980)MathSciNetCrossRefzbMATHGoogle Scholar
  19. [ST87]
    Srikanth, T.K., Toueg, S.: Simulating authenticated broadcasts to derive simple fault-tolerant algorithms. Distributed Computing 2(2), 80–94 (1987)CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Piyush Bansal
    • 1
  • Prasant Gopal
    • 2
  • Anuj Gupta
    • 1
  • Kannan Srinathan
    • 1
  • Pranav Kumar Vasishta
    • 1
  1. 1.Center for Security, Theory and Algorithmic ResearchIIITHyderabadIndia

Personalised recommendations