Paper 2023/1324

Fine-Grained Proxy Re-Encryption: Definitions & Constructions from LWE

Yunxiao Zhou, Shanghai Jiao Tong University
Shengli Liu, Shanghai Jiao Tong University
Shuai Han, Shanghai Jiao Tong University
Haibin Zhang, Beijing Institute of Technology
Abstract

Proxy re-encryption (PRE) allows a proxy with a re-encryption key to translate a ciphertext intended for Alice (delegator) to another ciphertext intended for Bob (delegatee) without revealing the underlying message. However, with PRE, Bob can obtain the whole message from the re-encrypted ciphertext, and Alice cannot take flexible control of the extent of the message transmitted to Bob. In this paper, we propose a new variant of PRE, called Fine-Grained PRE (FPRE), to support fine-grained re-encryptions. An FPRE is associated with a function family F, and each re-encryption key rk_{A→B}^f is associated with a function f ∈ F. With FPRE, Alice now can authorize re-encryption power to proxy by issuing rk_{A→B}^f to it, with f chosen by herself. Then the proxy can translate ciphertext encrypting m to Bob's ciphertext encrypting f(m) with such a fine-grained re-encryption key, and Bob only obtains a function of message m. In this way, Alice can take flexible control of the message spread by specifying functions. For FPRE, we formally define its syntax and formalize security notions including CPA security, ciphertext pseudo-randomness, unidirectionality, non-transitivity, collusion-safety under adaptive corruptions in the multi-user setting. Moreover, we propose a new security notion named ciphertext unlinkability, which blurs the link between a ciphertext and its re-encrypted ciphertext to hide the proxy connections between users. We establish the relations between those security notions. As for constructions, we propose two FPRE schemes, one for bounded linear functions and the other for deletion functions, based on the learning-with-errors (LWE) assumption. Our FPRE schemes achieve all the aforementioned desirable securities under adaptive corruptions in the standard model. As far as we know, our schemes provide the first solution to PRE with security under adaptive corruptions in the standard model.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
A minor revision of an IACR publication in ASIACRYPT 2023
Keywords
proxy re-encryptionfine-grained delegationunidirectionalitysingle-hopLWE
Contact author(s)
cloudzhou @ sjtu edu cn
slliu @ sjtu edu cn
dalen17 @ sjtu edu cn
bchainzhang @ aliyun com
History
2023-09-08: approved
2023-09-05: received
See all versions
Short URL
https://ia.cr/2023/1324
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2023/1324,
      author = {Yunxiao Zhou and Shengli Liu and Shuai Han and Haibin Zhang},
      title = {Fine-Grained Proxy Re-Encryption: Definitions & Constructions from {LWE}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2023/1324},
      year = {2023},
      url = {https://eprint.iacr.org/2023/1324}
}
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