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Paper 2016/1020

KDM Security for Identity-Based Encryption: Constructions and Separations

Yu Chen and Jiang Zhang and Yi Deng and Jinyong Chang

Abstract

For encryption schemes, key dependent message (KDM) security requires that ciphertexts preserve secrecy even when the encrypt messages may depend on the secret keys. While KDM security has been extensively studied for public-key encryption (PKE), it receives much less attention in the setting of identity-based encryption (IBE). In this work, we focus on the KDM security for IBE. Our results are threefold. We give a simple structure-mirroring PKE-to-IBE transformation via indistinguisha- bility obfuscation and puncturable PRFs. This transformation establishes a connec- tion between PKE and IBE in general. Particularly, it provides a liberal interface for transferring the KDM security results (both positive and negative) from PKE to IBE, though in the selective-identity sense. On the positive side, we present two constructions that achieve KDM security in the adaptive-identity sense for the first time. One is generically built from identity-based hash proof system (IB-HPS) with homomorphic property, which indicates that the IBE schemes of Gentry (Eurocrypt 2006), Coron (DCC 2009), Chow et al. (CCS 2010) are actually KDM-secure in the single-key setting. The other is built from indistinguishability obfuscation and a new notion named puncturable unique signature, which is bounded KDM-secure in the single-key setting. On the negative side, we separate n-circular security (which is a prototypical case of KDM security) from the standard IND-CPA/CCA security for IBE by giving a coun- terexample based on differing-inputs obfuscation and a new notion named puncturable IBE.

Note: We revised the security result of KDM-secure IBE from homomorphic IB-HPS.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint. MINOR revision.
Keywords
KDM securityIBEIB-HPSObfuscationCounterexample
Contact author(s)
yuchen prc @ gmail com; jiangzhang09 @ gmail com
History
2019-02-22: last of 5 revisions
2016-11-01: received
See all versions
Short URL
https://ia.cr/2016/1020
License
Creative Commons Attribution
CC BY
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