Idealizing Identity-Based Encryption
We formalize the standard application of identity-based encryption (IBE), namely non-interactive secure communication, as realizing an ideal system which we call delivery controlled channel (DCC). This system allows users to be registered (by a central authority) for an identity and to send messages securely to other users only known by their identity.
Quite surprisingly, we show that existing security definitions for IBE are not sufficient to realize DCC. In fact, it is impossible to do so in the standard model. We show, however, how to adjust any IBE scheme that satisfies the standard security definition IND-ID-CPA to achieve this goal in the random oracle model.
We also show that the impossibility result can be avoided in the standard model by considering a weaker ideal system that requires all users to be registered in an initial phase before any messages are sent. To achieve this, a weaker security notion, which we introduce and call IND-ID1-CPA, is actually sufficient. This justifies our new security definition and might open the door for more efficient schemes. We further investigate which ideal systems can be realized with schemes satisfying the standard notion and variants of selective security.
As a contribution of independent interest, we show how to model features of an ideal system that are potentially available to dishonest parties but not guaranteed, and which such features arise when using IBE.
KeywordsIdentity-based encryption Definitions Impossibility results Composability
Ueli Maurer was supported by the Swiss National Science Foundation (SNF), project no. 200020-132794. Dennis Hofheinz was supported by DFG grants HO 4534/2-2 and HO 4534/4-1.
- 1.Beaver, D.: Foundations of secure interactive computing. In: Feigenbaum, J. (ed.) CRYPTO 1991. LNCS, vol. 576, pp. 377–391. Springer, Heidelberg (1992) Google Scholar
- 2.Bellare, M., Rogaway, P.: Random oracles are practical: a paradigm for designing efficient protocols. In: Proceedings of the 1st ACM Conference on Computer and Communications Security, CCS 1993, pp. 62–73. ACM, New York (1993)Google Scholar
- 5.Canetti, R.: Universally composable security: a new paradigm for cryptographic protocols. In: Proceedings of FOCS 2001, pp. 136–145. IEEE Computer Society (2001)Google Scholar
- 8.Coretti, S., Maurer, U., Tackmann, B.: Constructing confidential channels from authenticated channelspublic-key encryption revisited. In: Sako, K., Sarkar, P. (eds.) Advances in Cryptology - ASIACRYPT 2013. Lecture Notes in Computer Science, vol. 8269, pp. 134–153. Springer, Heidelberg (2013)CrossRefGoogle Scholar
- 9.Gentry, C., Peikert, C., Vaikuntanathan, V.: Trapdoors for hard lattices and new cryptographic constructions. In: Proceedings of STOC 2008, pp. 197–206. ACM (2008)Google Scholar
- 10.Goldreich, O., Micali, S., Wigderson, A.: How to play any mental game or a completeness theorem for protocols with honest majority. In: Proceedings of STOC 1987, pp. 218–229. ACM (1987)Google Scholar
- 11.Matt, C., Maurer, U.: A definitional framework for functional encryption. Cryptology ePrint Archive, Report 2013/559 (2013)Google Scholar
- 13.Maurer, U., Renner, R.: Abstract cryptography. In: Chazelle, B. (ed.) The Second Symposium on Innovations in Computer Science, ICS 2011, pp. 1–21. Tsinghua University Press January 2011Google Scholar
- 14.Maurer, U.M., Yacobi, Y.: Non-interative public-key cryptography. In: Davies, D.W. (ed.) EUROCRYPT 1991. LNCS, vol. 547, pp. 498–507. Springer, Heidelberg (1991) Google Scholar
- 15.Micali, S., Rogaway, P.: Secure computation. In: Feigenbaum, J. (ed.) CRYPTO 1991. LNCS, vol. 576, pp. 392–404. Springer, Heidelberg (1992) Google Scholar
- 16.Naor, M., Yung, M.: Public-key cryptosystems provably secure against chosen ciphertext attacks. In: STOC, pp. 427–437. ACM (1990)Google Scholar
- 19.Pfitzmann, B., Waidner, M.: A model for asynchronous reactive systems and its application to secure message transmission. In: Proceedings of IEEE Symposium on Security and Privacy 2001, pp. 184–200. IEEE Computer Society (2001)Google Scholar