Watermarking Cryptographic Capabilities
Author(s)
Cohen, Aloni(Aloni Jonathan); Holmgren, Justin Lee; Nishimaki, Ryo; Vaikuntanathan, Vinod; Wichs, Daniel
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A watermarking scheme for programs embeds some information called a mark into a program while preserving its functionality. No adversary can remove the mark without damaging the functionality of the program. In this work, we study the problem of watermarking various cryptographic programs such as pseudorandom function (PRF) evaluation, decryption, and signing. For example, given a PRF F, we create a marked program C that evaluates F(·). An adversary that gets C cannot come up with any program C ∗ in which the mark is removed but which still evaluates the PRF correctly on even a small fraction of the inputs. The work of Barak et al. [CRYPTO 2001, Springer, Berlin, 2001, pp. 1-18; J. ACM, 59 (2012), 6] shows that, assuming indistinguishability obfuscation (iO), such watermarking is impossible if the marked program C evaluates the original program with perfect correctness. In this work we show that, assuming iO, such watermarking is possible if the marked program C is allowed to err with even a negligible probability, which would be undetectable to the user. We also significantly extend the impossibility results to our relaxed setting. Our watermarking schemes are public key, meaning that we use a secret marking key to embed marks in programs, and a public detection key that allows anyone to detect marks in programs. Our schemes are secure against chosen program attacks where the adversary is given oracle access to the marking functionality. We emphasize that our security notion of watermark nonremovability considers arbitrary adversarial strategies to modify the marked program, in contrast to the prior works. ©2018 Society for Industrial and Applied Mathematics
Date issued
2018-12Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science; Massachusetts Institute of Technology. Computer Science and Artificial Intelligence LaboratoryJournal
SIAM Journal on Computing
Publisher
Society for Industrial & Applied Mathematics (SIAM)
Citation
Cohen, Aloni et al., "Watermarking Cryptographic Capabilities." SIAM Journal on Computing 47, 6 (December 2018): 2157–2202 doi. 10.1137/18M1164834 ©2018 Authors
Version: Final published version
ISSN
1095-7111