Paper 2022/1429

Collusion Resistant Copy-Protection for Watermarkable Functionalities

Jiahui Liu, The University of Texas at Austin
Qipeng Liu, Simons Institute for the Theory of Computing
Luowen Qian, Boston University
Mark Zhandry, Princeton University & NTT Research

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: (*) The feasibility of copy-protecting all watermarkable functionalities is an open question raised by Aaronson et al. (CRYPTO' 21). In the literature, watermarking decryption, digital signature schemes and PRFs have been extensively studied. For the first time, we show that digital signature schemes can be copy-protected. Together with the previous work on copy-protection of decryption and PRFs by Coladangelo et al. (CRYPTO' 21), it suggests that many watermarkable functionalities can be copy-protected, partially answering the above open question by Aaronson et al. (*) We make all the above schemes (copy-protection of decryption, digital signatures, and PRFs) k bounded collusion resistant for any polynomial k, giving the first bounded collusion resistant copy-protection for various functionalities in the plain model.

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Publication info
A minor revision of an IACR publication in TCC 2022
quantum cryptography quantum copy protection unclonable cryptography collusion resistance watermarking
Contact author(s)
jiahui @ utexas edu
qipengliu0 @ gmail com
luowenq @ bu edu
mzhandry @ gmail com
2022-11-13: revised
2022-10-20: received
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Creative Commons Attribution


      author = {Jiahui Liu and Qipeng Liu and Luowen Qian and Mark Zhandry},
      title = {Collusion Resistant Copy-Protection for Watermarkable Functionalities},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1429},
      year = {2022},
      note = {\url{}},
      url = {}
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