On the limitations of the spread of an IBE-to-PKE transformation.

*(English)*Zbl 1151.94526
Yung, Moti (ed.) et al., Public key cryptography – PKC 2006. 9th international conference on theory and practice of public-key cryptography, New York, NY, USA, April 24–26, 2006. Proceedings. Berlin: Springer (ISBN 3-540-33851-9/pbk). Lecture Notes in Computer Science 3958, 274-289 (2006).

Summary: By a generic transformation by R. Canetti, S. Halevi and J. Katz [Advances in cryptology – EUROCRYPT 2004. Lect. Notes Comput. Sci. 3027, 207–222 (2004; Zbl 1122.94358)] (CHK) every Identity-based encryption (IBE) scheme implies a chosen-ciphertext secure public-key encryption (PKE) scheme. In the same work it is claimed that this transformation maps the two existing IBE schemes to two new and different chosen-ciphertext secure encryption schemes, each with individual advantages over the other.

In this work we reconsider one of the two specific instantiations of the CHK transformation (when applied to the “second Boneh/Boyen IBE scheme”). We demonstrate that by applying further simplifications the resulting scheme can be proven secure under a weaker assumption than the underlying IBE scheme.

Surprisingly, our simplified scheme nearly converges to a recent encryption scheme due to Boyen, Mei, and Waters which itself was obtained from the other specific instantiation of the CHK transformation (when applied to the ”first Boneh/Boyen IBE scheme”). We find this particularly interesting since the two underlying IBE schemes are completely different.

The bottom line of this paper is that the claim made by Canetti, Halevi, and Katz needs to be reformulated to: the CHK transformation maps the two known IBE schemes to nearly one single encryption scheme.

For the entire collection see [Zbl 1102.94003].

In this work we reconsider one of the two specific instantiations of the CHK transformation (when applied to the “second Boneh/Boyen IBE scheme”). We demonstrate that by applying further simplifications the resulting scheme can be proven secure under a weaker assumption than the underlying IBE scheme.

Surprisingly, our simplified scheme nearly converges to a recent encryption scheme due to Boyen, Mei, and Waters which itself was obtained from the other specific instantiation of the CHK transformation (when applied to the ”first Boneh/Boyen IBE scheme”). We find this particularly interesting since the two underlying IBE schemes are completely different.

The bottom line of this paper is that the claim made by Canetti, Halevi, and Katz needs to be reformulated to: the CHK transformation maps the two known IBE schemes to nearly one single encryption scheme.

For the entire collection see [Zbl 1102.94003].