Cryptology ePrint Archive: Report 2015/827

Unbounded Hierarchical Identity-Based Encryption with Efficient Revocation

Geumsook Ryu and Kwangsu Lee and Seunghwan Park and Dong Hoon Lee

Abstract: Hierarchical identity-based encryption (HIBE) is an extension of identity-based encryption (IBE) where an identity of a user is organized as a hierarchical structure and a user can delegate the private key generation to another user. Providing a revocation mechanism for HIBE is highly necessary to keep a system securely. Revocable HIBE (RHIBE) is an HIBE scheme that can revoke a user's private key if his credential is expired or revealed. In this paper, we first propose an unbounded HIBE scheme where the maximum hierarchy depth is not limited and prove its selective security under a q-type assumption. Next, we propose an efficient unbounded RHIBE scheme by combining our unbounded HIBE scheme and a binary tree structure, and then we prove its selective security. By presenting the unbounded RHIBE scheme, we solve the open problem of Seo and Emura in CT-RSA 2015.

Category / Keywords: public-key cryptography / Hierarchical identity-based encryption, Revocation, Unbounded hierarchy depth, Bilinear maps

Date: received 25 Aug 2015

Contact author: madeby_r at korea ac kr; guspin@korea ac kr

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Version: 20150826:145523 (All versions of this report)

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