Reducing Honest Re-Encryption Attack to Chosen Ciphertext Attack

Haotian Yin; Jie Zhang; Wanxin Li; Yuji Dong; Eng Gee Lim; Dominik Wojtczak

Paper 2025/704

Reducing Honest Re-Encryption Attack to Chosen Ciphertext Attack

Haotian Yin

, School of Advanced Technology, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China

Jie Zhang, School of Advanced Technology, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China

Wanxin Li, School of Advanced Technology, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China

Yuji Dong, School of Internet of Things, Xi'an Jiaotong-Liverpool University, Suzhou, 215400, China

Eng Gee Lim, School of Advanced Technology, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China

Dominik Wojtczak, Department of Computer Science, University of Liverpool, Liverpool, L69 3BX, UK

Abstract

Proxy re-encryption (PRE) schemes allow a delegator to designate a proxy to re-encrypt its ciphertext into a ciphertext that the delegatee can decrypt. In contrast, the proxy gains nothing helpful from this transformation. This decryption-power transfer is proper in applications of encrypted email forwarding, key escrow, and publish/subscribe systems. The security notions for PRE are inherited from the standard public key encryption (PKE) schemes, i.e., indistinguishability under chosen-plaintext attacks (CPA) and security under chosen-ciphertext attacks (CCA). A recently popular notion, indistinguishability under honest re-encryption attacks (HRA), was proposed by Cohen in 2019, indicating that CPA security is insufficient for PRE because some CPA-secure PRE leaks the secret key of the delegator. Many post-quantum secure PRE schemes have recently been designed under the HRA security model. However, HRA security differs from traditional CCA security, and there is no known reduction between them. The existing results show they appear to be incompatible. This paper aims to bridge those two security notions via reductions. In addition, we found that many existing HRA-secure schemes are vulnerable to collusion. We provide a generic transformation from a CPA-secure PRE to a collusion-resistant and CPA-secure PRE. This transformation also applies to HRA-secure PREs.

Metadata

Available format(s): PDF
Category: Public-key cryptography
Publication info: Preprint.
Keywords: Proxy re-encryption Honest re-encryption attack Collusion resistance
Contact author(s): haotian yin23 @ student xjtlu edu cn
History: 2025-04-18: approved; 2025-04-18: received; See all versions
Short URL: https://ia.cr/2025/704
License: CC BY

BibTeX

@misc{cryptoeprint:2025/704,
      author = {Haotian Yin and Jie Zhang and Wanxin Li and Yuji Dong and Eng Gee Lim and Dominik Wojtczak},
      title = {Reducing Honest Re-Encryption Attack to Chosen Ciphertext Attack},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/704},
      year = {2025},
      url = {https://eprint.iacr.org/2025/704}
}