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Paper 2021/1261

Identity-Based Encryption for Fair Anonymity Applications: Defining, Implementing, and Applying Rerandomizable RCCA-secure IBE

Yi Wang and Rongmao Chen and Xinyi Huang and Jianting Ning and Baosheng Wang and Moti Yung

Abstract

Our context is anonymous encryption schemes hiding their receiver, but in a setting which allows authorities to reveal the receiver when needed. While anonymous Identity-Based Encryption (IBE) is a natural candidate for such fair anonymity (it gives trusted authority access by design), the de facto security standard (a.k.a. IND-ID-CCA) is incompatible with the ciphertext rerandomizability which is crucial to anonymous communication. Thus, we seek to extend IND-ID-CCA security for IBE to a notion that can be meaningfully relaxed for rerandomizability while it still protects against active adversaries. To the end, inspired by the notion of replayable adaptive chosen-ciphertext attack (RCCA) security (Canetti et al., Crypto'03), we formalize a new security notion called Anonymous Identity-Based RCCA (ANON-ID-RCCA) security for rerandomizable IBE and propose the first construction with rigorous security analysis. The core of our scheme is a novel extension of the double-strand paradigm, which was originally proposed by Golle et al. (CT-RSA'04) and later extended by Prabhakaran and Rosulek (Crypto'07), to the well-known Gentry-IBE (Eurocrypt'06). Notably, our scheme is the first IBE that simultaneously satisfies adaptive security, rerandomizability, and recipient-anonymity to date. As the application of our new notion, we design a new universal mixnet in the identity-based setting that does not require public key distribution (with fair anonymity). More generally, our new notion is also applicable to most existing rerandomizable RCCA-secure applications to eliminate the need for public key distribution infrastructure while allowing fairness.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
A minor revision of an IACR publication in ASIACRYPT 2021
Keywords
RCCA securityidentity-based encryptionrerandomizability
Contact author(s)
wangyi14 @ nudt edu cn
History
2021-09-21: received
Short URL
https://ia.cr/2021/1261
License
Creative Commons Attribution
CC BY
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