Cryptology ePrint Archive: Report 2015/1254

Identity-based Hierarchical Key-insulated Encryption without Random Oracles

Yohei Watanabe and Junji Shikata

Abstract: Key-insulated encryption is one of the effective solutions to a key exposure problem. At Asiacrypt'05, Hanaoka et al. proposed an identity-based hierarchical key-insulated encryption (hierarchical IKE) scheme. Although their scheme is secure in the random oracle model, it has a ``hierarchical key-updating structure,'' which is attractive functionality that enhances key exposure resistance.

In this paper, we first propose the hierarchical IKE scheme without random oracles. Our hierarchical IKE scheme is secure under the symmetric external Diffie-Hellman (SXDH) assumption, which is known as the simple and static one. Particularly, in the non-hierarchical case, our construction is the first IKE scheme that achieves constant-size parameters including public parameters, secret keys, and ciphertexts.

Furthermore, we also propose the first public-key-based key-insulated encryption (PK-KIE) in the hierarchical setting by using our technique.

Category / Keywords: public-key cryptography / Key-insulated encryption, Identity-based hierarchical key-insulated encryption, Hierarchical identity-based encryption, Asymmetric pairing

Original Publication (with minor differences): IACR-PKC-2016

Date: received 2 Jan 2016, last revised 4 Jan 2017

Contact author: watanabe at uec ac jp

Available format(s): PDF | BibTeX Citation

Note: Modified constructions and security proofs due to bugs in the proofs.

Version: 20170105:061432 (All versions of this report)

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