International Association for Cryptologic Research

International Association
for Cryptologic Research


Collusion-Resistant Copy-Protection for Watermarkable Functionalities

Jiahui Liu , University of Texas at Austin
Qipeng Liu , Simons Institute for the Theory of Computing
Luowen Qian , Boston University
Mark Zhandry , NTT Research and Princeton University
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Presentation: Slides
Conference: TCC 2022
Abstract: Copy-protection is the task of encoding a program into a quantum state to prevent illegal duplications. A line of recent works studied copy-protection schemes under "1 -> 2 attacks": the adversary receiving one program copy can not produce two valid copies. However, under most circumstances, vendors need to sell more than one copy of a program and still ensure that no duplicates can be generated. In this work, we initiate the study of collusion-resistant copy-protection in the plain model. Our results are twofold: * For the first time, we show that all major watermarkable functionalities can be copy-protected (including unclonable decryption, digital signatures, and PRFs). Among these, copy-protection of digital signature schemes is not known before. The feasibility of copy-protecting all watermarkable functionalities is an open question raised by Aaronson et al. (CRYPTO' 21) * We make all the above schemes k bounded collusion-resistant for any polynomial k, giving the first bounded collusion-resistant copy-protection for various functionalities in the plain model.
  title={Collusion-Resistant Copy-Protection for Watermarkable Functionalities},
  author={Jiahui Liu and Qipeng Liu and Luowen Qian and Mark Zhandry},