Space-Efficient Private Search with Applications to Rateless Codes

  • George Danezis
  • Claudia Diaz
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4886)


Private keyword search is a technique that allows for searching and retrieving documents matching certain keywords without revealing the search criteria. We improve the space efficiency of the Ostrovsky et al. Private Search [9] scheme, by describing methods that require considerably shorter buffers for returning the results of the search. Our basic decoding scheme recursive extraction, requires buffers of length less than twice the number of returned results and is still simple and highly efficient. Our extended decoding schemes rely on solving systems of simultaneous equations, and in special cases can uncover documents in buffers that are close to 95% full. Finally we note the similarity between our decoding techniques and the ones used to decode rateless codes, and show how such codes can be extracted from encrypted documents.


Dine Mellon 


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  1. 1.
    Bethencourt, J., Song, D., Waters, B.: New constructions and practical applications for private stream searching (extended abstract). In: SP 2006. Proceedings of the 2006 IEEE Symposium on Security and Privacy, Washington, DC, USA, pp. 132–139. IEEE Computer Society Press, Los Alamitos (2006)Google Scholar
  2. 2.
    Bethencourt, J., Song, D., Waters, B.: New techniques for private stream searching. Technical report, Carnegie Mellon University (2006)Google Scholar
  3. 3.
    Bloom, B.H.: Space/time trade-offs in hash coding with allowable errors. Commun. ACM 13(7), 422–426 (1970)CrossRefMATHGoogle Scholar
  4. 4.
    Chaum, D.: The dining cryptographers problem: Unconditional sender and recipient untraceability. Journal of Cryptology 1, 65–75 (1988)CrossRefMATHMathSciNetGoogle Scholar
  5. 5.
    Danezis, G., Diaz, C.: Improving the decoding efficiency of private search. Dagstuhl Seminar on Anonymity and its Applications (October 2005)Google Scholar
  6. 6.
    Gamal, T.E.: A public key cryptosystem and a signature scheme based on discrete logarithms. In: Blakely, G.R., Chaum, D. (eds.) CRYPTO 1984. LNCS, vol. 196, pp. 10–18. Springer, Heidelberg (1985)CrossRefGoogle Scholar
  7. 7.
    Maymounkov, P.: Online codes. Technical report, New York University (2003)Google Scholar
  8. 8.
    Maymounkov, P., Mazieres, D.: Rateless codes and big downloads. In: Kaashoek, M.F., Stoica, I. (eds.) IPTPS 2003. LNCS, vol. 2735, pp. 247–255. Springer, Heidelberg (2003)CrossRefGoogle Scholar
  9. 9.
    Ostrovsky, R., Skeith III, W.E.: Private searching on streaming data. In: Shoup, V. (ed.) CRYPTO 2005. LNCS, vol. 3621, pp. 223–240. Springer, Heidelberg (2005)CrossRefGoogle Scholar
  10. 10.
    Paillier, P.: Public-key cryptosystems based on composite degree residuosity classes. In: Stern, J. (ed.) EUROCRYPT 1999. LNCS, vol. 1592, pp. 223–238. Springer, Heidelberg (1999)CrossRefGoogle Scholar
  11. 11.
    Sassaman, L., Cohen, B., Mathewson, N.: The pynchon gate: A secure method of pseudonymous mail retrieval. In: Proceedings of the Workshop on Privacy in the Electronic Society (WPES 2005), Arlington, VA, USA (November 2005)Google Scholar
  12. 12.
    Serjantov, A.: Anonymizing censorship resistant systems. In: Druschel, P., Kaashoek, M.F., Rowstron, A. (eds.) IPTPS 2002. LNCS, vol. 2429, Springer, Heidelberg (2002)CrossRefGoogle Scholar
  13. 13.
    Waidner, M., Pfitzmann, B.: The dining cryptographers in the disco: Unconditional sender and recipient untraceability with computationally secure servicability. In: Quisquater, J.-J., Vandewalle, J. (eds.) EUROCRYPT 1989. LNCS, vol. 434, Springer, Heidelberg (1990)Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2007

Authors and Affiliations

  • George Danezis
    • 1
  • Claudia Diaz
    • 1
  1. 1.K.U. LeuvenESAT/COSICLeuven-HeverleeBelgium

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