### Efficient Identity-Based Encryption with Hierarchical Key-Insulation from HIBE

Keita Emura, Atsushi Takayasu, and Yohei Watanabe

##### Abstract

Hierarchical key-insulated identity-based encryption (HKIBE) is identity-based encryption (IBE) that allows users to update their secret keys to achieve (hierarchical) key-exposure resilience, which is an important notion in practice. However, existing HKIBE constructions have limitations in efficiency: sizes of ciphertexts and secret keys depend on the hierarchical depth. In this paper, we first triumph over the barrier by proposing simple but effective design methodologies to construct efficient HKIBE schemes. First, we show a generic construction from any hierarchical IBE (HIBE) scheme that satisfies a special requirement, called MSK evaluatability introduced by Emura et al. (Designs, Codes and Cryptography, 2021). It provides several new and efficient instantiations since most pairing-based HIBE schemes satisfy the requirement. It is worth noting that it preserves all parameters' sizes of the underlying HIBE scheme, and hence we obtain several efficient HKIBE schemes under the $k$-linear assumption in the standard model. Since MSK evaluatability is dedicated to pairing-based HIBE schemes, the first construction restricts pairing-based instantiations. To realize efficient instantiation from various assumptions, we next propose a generic construction of an HKIBE scheme from any plain HIBE scheme. It is based on Hanaoka et al.'s HKIBE scheme (Asiacrypt 2005), and does not need any special properties. Therefore, we obtain new efficient instantiations from various assumptions other than pairing-oriented ones. Though the sizes of secret keys and ciphertexts are larger than those of the first construction, it is more efficient than Hanaoka et al.'s scheme in the sense of the sizes of master public/secret keys.

Note: Fixed typos and minor issues.

Available format(s)
Category
Public-key cryptography
Publication info
Published elsewhere. Designs, Codes and Cryptography
DOI
10.1007/s10623-021-00926-z
Contact author(s)
k-emura @ nict go jp
takayasu @ nict go jp
watanabe @ uec ac jp
History
2021-08-24: revised
See all versions
Short URL
https://ia.cr/2020/1087

CC BY

BibTeX

@misc{cryptoeprint:2020/1087,
author = {Keita Emura and Atsushi Takayasu and Yohei Watanabe},
title = {Efficient Identity-Based Encryption with Hierarchical Key-Insulation from HIBE},
howpublished = {Cryptology ePrint Archive, Paper 2020/1087},
year = {2020},
doi = {10.1007/s10623-021-00926-z},
note = {\url{https://eprint.iacr.org/2020/1087}},
url = {https://eprint.iacr.org/2020/1087}
}
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