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

Yi Wang, Rongmao Chen, Xinyi Huang, Jianting Ning, 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.

Available format(s)
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
Short URL
https://ia.cr/2021/1261

CC BY

BibTeX

@misc{cryptoeprint:2021/1261,
author = {Yi Wang and Rongmao Chen and Xinyi Huang and Jianting Ning and Baosheng Wang and Moti Yung},
title = {Identity-Based Encryption for Fair Anonymity Applications:  Defining, Implementing, and Applying Rerandomizable RCCA-secure IBE},
howpublished = {Cryptology ePrint Archive, Paper 2021/1261},
year = {2021},
note = {\url{https://eprint.iacr.org/2021/1261}},
url = {https://eprint.iacr.org/2021/1261}
}

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