Advertisement

Bidirectional Asynchronous Ratcheted Key Agreement with Linear Complexity

  • F. Betül Durak
  • Serge VaudenayEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11689)

Abstract

Following up mass surveillance and privacy issues, modern secure communication protocols now seek more security such as forward secrecy and post-compromise security. They cannot rely on an assumption such as synchronization, predictable sender/receiver roles, or online availability. Ratcheting was introduced to address forward secrecy and post-compromise security in real-world messaging protocols. At CSF 2016 and CRYPTO 2017, ratcheting was studied either without zero round-trip time (0-RTT) or without bidirectional communication. At CRYPTO 2018, ratcheting with bidirectional communication was done using heavy key-update primitives. At EUROCRYPT 2019, another protocol was proposed. All those protocols use random oracles. Furthermore, exchanging Open image in new window messages has complexity Open image in new window in general.

In this work, we define the bidirectional asynchronous ratcheted key agreement ( Open image in new window ) with formal security notions. We provide a simple security model and design a secure Open image in new window scheme using no key-update primitives, no random oracle, an with Open image in new window complexity. It is based on a public-key cryptosystem, a signature scheme, one-time symmetric encryption, and a collision-resistant hash function family. We further show that Open image in new window (even unidirectional) implies public-key cryptography, meaning that it cannot solely rely on symmetric cryptography.

Notes

Acknowledgements

We thank Joseph Jaeger for his valuable comments to the first version of this paper. We thank Paul Rösler for insightful discussions and comments. We also owe to Andrea Caforio for his implementation results.

References

  1. 1.
    Alwen, J., Coretti, S., Dodis, Y.: The double ratchet: security notions, proofs, and modularization for the signal protocol. In: Ishai, Y., Rijmen, V. (eds.) EUROCRYPT 2019. LNCS, vol. 11476, pp. 129–158. Springer, Cham (2019).  https://doi.org/10.1007/978-3-030-17653-2_5. Full version: https://eprint.iacr.org/2018/1037.pdfCrossRefGoogle Scholar
  2. 2.
    Bellare, M., Singh, A.C., Jaeger, J., Nyayapati, M., Stepanovs, I.: Ratcheted encryption and key exchange: the security of messaging. In: Katz, J., Shacham, H. (eds.) CRYPTO 2017. LNCS, vol. 10403, pp. 619–650. Springer, Cham (2017).  https://doi.org/10.1007/978-3-319-63697-9_21CrossRefGoogle Scholar
  3. 3.
    Borisov, N., Goldberg, I., Brewer, E.: Off-the-record communication, or, why not to use PGP. In: Proceedings of the 2004 ACM Workshop on Privacy in the Electronic Society, WPES 2004, pp. 77–84. ACM, New York (2004)Google Scholar
  4. 4.
    Canetti, R., Krawczyk, H.: Analysis of key-exchange protocols and their use for building secure channels. In: Pfitzmann, B. (ed.) EUROCRYPT 2001. LNCS, vol. 2045, pp. 453–474. Springer, Heidelberg (2001).  https://doi.org/10.1007/3-540-44987-6_28CrossRefGoogle Scholar
  5. 5.
    Cohn-Gordon, K., Cremers, C., Dowling, B., Garratt, L., Stebila, D.: A formal security analysis of the signal messaging protocol. In: 2017 IEEE European Symposium on Security and Privacy (EuroS&P), pp. 451–466, April 2017Google Scholar
  6. 6.
    Cohn-Gordon, K., Cremers, C., Garratt, L.: On post-compromise security. In: 2016 IEEE 29th Computer Security Foundations Symposium (CSF), pp. 164–178, June 2016Google Scholar
  7. 7.
    Derler, D., Jager, T., Slamanig, D., Striecks, C.: Bloom filter encryption and applications to efficient forward-secret 0-RTT key exchange. In: Nielsen, J.B., Rijmen, V. (eds.) EUROCRYPT 2018. LNCS, vol. 10822, pp. 425–455. Springer, Cham (2018).  https://doi.org/10.1007/978-3-319-78372-7_14CrossRefGoogle Scholar
  8. 8.
    Betül Durak, F., Vaudenay, S.: Bidirectional asynchronous ratcheted key agreement with linear complexity. https://eprint.iacr.org/2018/889.pdf
  9. 9.
    Günther, F., Hale, B., Jager, T., Lauer, S.: 0-RTT key exchange with full forward secrecy. In: Coron, J.-S., Nielsen, J.B. (eds.) EUROCRYPT 2017. LNCS, vol. 10212, pp. 519–548. Springer, Cham (2017).  https://doi.org/10.1007/978-3-319-56617-7_18CrossRefGoogle Scholar
  10. 10.
    Jaeger, J., Stepanovs, I.: Optimal channel security against fine-grained state compromise: the safety of messaging. In: Shacham, H., Boldyreva, A. (eds.) CRYPTO 2018. LNCS, vol. 10991, pp. 33–62. Springer, Cham (2018).  https://doi.org/10.1007/978-3-319-96884-1_2. Full version: https://eprint.iacr.org/2018/553.pdfCrossRefGoogle Scholar
  11. 11.
    Jost, D., Maurer, U., Mularczyk, M.: Efficient ratcheting: almost-optimal guarantees for secure messaging. In: Ishai, Y., Rijmen, V. (eds.) EUROCRYPT 2019. LNCS, vol. 11476, pp. 159–188. Springer, Cham (2019).  https://doi.org/10.1007/978-3-030-17653-2_6. Full version: https://eprint.iacr.org/2018/954.pdfCrossRefGoogle Scholar
  12. 12.
    LaMacchia, B., Lauter, K., Mityagin, A.: Stronger security of authenticated key exchange. In: Susilo, W., Liu, J.K., Mu, Y. (eds.) ProvSec 2007. LNCS, vol. 4784, pp. 1–16. Springer, Heidelberg (2007).  https://doi.org/10.1007/978-3-540-75670-5_1CrossRefzbMATHGoogle Scholar
  13. 13.
    Ohkubo, M., Suzuki, K., Kinoshita, S.: Cryptographic approach to “privacy-friendly” tags. In: RFID Privacy Workshop (2003)Google Scholar
  14. 14.
    Ohkubo, M., Suzuki, K., Kinoshita, S.: Efficient hash-chain based RFID privacy protection scheme. In: International Conference on Ubiquitous Computing (Ubicomp), Workshop Privacy: Current Status and Future Directions (2004)Google Scholar
  15. 15.
    Poettering, B., Rösler, P.: Towards bidirectional ratcheted key exchange. In: Shacham, H., Boldyreva, A. (eds.) CRYPTO 2018. LNCS, vol. 10991, pp. 3–32. Springer, Cham (2018).  https://doi.org/10.1007/978-3-319-96884-1_1. Full version: https://eprint.iacr.org/2018/296.pdfCrossRefGoogle Scholar
  16. 16.
    Open Whisper Systems. Signal protocol library for Java/Android. GitHub repository (2017). https://github.com/WhisperSystems/libsignal-protocol-java
  17. 17.
    Unger, N., et al.: SoK: secure messaging. In: 2015 IEEE Symposium on Security and Privacy, pp. 232–249, May 2015Google Scholar
  18. 18.
    WhatsApp. Whatsapp encryption overview. Technical white paper (2016). https://www.whatsapp.com/security/WhatsApp-Security-Whitepaper.pdf

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Robert Bosch LLC - Research and Technology CenterPittsburghUSA
  2. 2.Ecole Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland

Personalised recommendations