### Adaptively Secure Lattice-based Revocable IBE in the QROM: Compact Parameters, Tight Security, and Anonymity

Atsushi Takayasu

##### Abstract

Revocable identity-based encryption (RIBE) is an extension of IBE that satisfies a key revocation mechanism to manage a number of users dynamically and efficiently. To resist quantum attacks, two adaptively secure lattice-based RIBE schemes are known in the (quantum) random oracle model ((Q)ROM). Wang et al.'s scheme that is secure in the ROM has large secret keys depending on the depth of a binary tree and its security reduction is not tight. Ma and Lin's scheme that is secure in the QROM has large ciphertexts depending on the length of identities and is not anonymous. In this paper, we propose an adaptively secure lattice-based RIBE scheme that is secure in the QROM. Our scheme has compact parameters, where the ciphertext-size is smaller than Wang et al.'s scheme and the secret key size is the same as Ma and Lin's scheme. Moreover, our scheme is anonymous and its security reduction is completely tight. We design the proposed scheme by modifying Ma-Lin's scheme instantiated by the Gentry-Peikert-Vaikuntanathan (GPV) IBE. We can obtain the advantages of our scheme by making use of Katsumata et al.'s proof technique of the GPV IBE in the QROM.

Available format(s)
Category
Public-key cryptography
Publication info
Published elsewhere. Minor revision.Designs, Codes and Cryptography
Contact author(s)
takayasu @ nict go jp
History
Short URL
https://ia.cr/2021/695

CC BY

BibTeX

@misc{cryptoeprint:2021/695,
author = {Atsushi Takayasu},
title = {Adaptively Secure Lattice-based Revocable IBE in the QROM: Compact Parameters, Tight Security, and Anonymity},
howpublished = {Cryptology ePrint Archive, Paper 2021/695},
year = {2021},
note = {\url{https://eprint.iacr.org/2021/695}},
url = {https://eprint.iacr.org/2021/695}
}

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