Paper 2022/1422

Unlinkable Policy-based Sanitizable Signatures

Ismail Afia, University of Victoria
Riham AlTawy, University of Victoria
Abstract

In CT-RSA 2020, P3S was proposed as the first policy-based sanitizable signature scheme which allows the signer to designate future message sanitizers by defining an access policy relative to their attributes rather than their keys. However, since P3S utilizes a policy-based chameleon hash (PCH), it does not achieve unlinkability which is a required notion in privacy-preserving applications. Moreover, P3S requires running a procedure to share the secret trapdoor information for PCH with each new sanitizer before sanitizing a new message. We further observe that in order to maintain the transparency in P3S’s multiple-sanitizers setting, the signature size should grow linearly with the number of sanitizers. In this work, we propose an unlinkable policy-based sanitizable signature scheme (UP3S) where we employ a rerandomizable digital signature scheme and a traceable attribute-based signature scheme as its building blocks. Compared to P3S, UP3S achieves unlinkability, does not require new secrets to be shared with future sanitizers prior to sanitizing each message, and has a fixed signature size for a given sanitization policy. We define and formally prove the security notions of the generic scheme, propose an instantiation of UP3S utilizing the Pointcheval-Sanders rerandomizable signature scheme and DTABS traceable attribute-based signature scheme, and analyze its efficiency. Finally, we compare UP3S with P3S in terms of the features of the procedures, scalability, and security models.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Published elsewhere. CT-RSA 2023
Keywords
sanitizable signatureattribute-based signaturesrerandomizable signaturespolicy-based signature
Contact author(s)
iafia @ uvic ca
raltawy @ uvic ca
History
2023-02-13: revised
2022-10-19: received
See all versions
Short URL
https://ia.cr/2022/1422
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2022/1422,
      author = {Ismail Afia and Riham AlTawy},
      title = {Unlinkable Policy-based Sanitizable Signatures},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1422},
      year = {2022},
      note = {\url{https://eprint.iacr.org/2022/1422}},
      url = {https://eprint.iacr.org/2022/1422}
}
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