### Efficient Invisible and Unlinkable Sanitizable Signatures

Xavier Bultel, Pascal Lafourcade, Russell W. F. Lai, Giulio Malavolta, Dominique Schröder, and Sri Aravinda Krishnan Thyagarajan

##### Abstract

Sanitizable signatures allow designated parties (the sanitizers) to apply arbitrary modifications to some restricted parts of signed messages. A secure scheme should not only be unforgeable, but also protect privacy and hold both the signer and the sanitizer accountable. Two important security properties that are seemingly difficult to achieve simultaneously and efficiently are invisibility and unlinkability. While invisibility ensures that the admissible modifications are hidden from external parties, unlinkability says that sanitized signatures cannot be linked to their sources. Achieving both properties simultaneously is crucial for applications where sensitive personal data is signed with respect to data-dependent admissible modifications. The existence of an efficient construction achieving both properties was recently posed as an open question by Camenisch et al. (PKC’17). In this work, we propose a solution to this problem with a two-step construction. First, we construct (non-accountable) invisible and unlinkable sanitizable signatures from signatures on equivalence classes and other basic primitives. Second, we put forth a generic transformation using verifiable ring signatures to turn any non-accountable sanitizable signature into an accountable one while preserving all other properties. When instantiating in the generic group and random oracle model, the efficiency of our construction is comparable to that of prior constructions, while providing stronger security guarantees.

Available format(s)
Category
Public-key cryptography
Publication info
A minor revision of an IACR publication in PKC 2019
Contact author(s)
xavier bultel @ uca fr
russell lai @ cs fau de
giulio malavolta @ hotmail it
dominique schroeder @ fau de
sri aravinda krishnan thyagarajan @ cs fau de
History
Short URL
https://ia.cr/2019/648

CC BY

BibTeX

@misc{cryptoeprint:2019/648,
author = {Xavier Bultel and Pascal Lafourcade and Russell W.  F.  Lai and Giulio Malavolta and Dominique Schröder and Sri Aravinda Krishnan Thyagarajan},
title = {Efficient Invisible and Unlinkable Sanitizable Signatures},
howpublished = {Cryptology ePrint Archive, Paper 2019/648},
year = {2019},
note = {\url{https://eprint.iacr.org/2019/648}},
url = {https://eprint.iacr.org/2019/648}
}

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