## Private Constrained PRFsA constrained pseudorandom function (PRF) is a PRF for which one can generate
constrained keys that can only be used to evaluate the PRF on a subset of the
domain. In this work, we introduce the notion of a ## Constraining Pseudorandom Functions Privately
Abstract:
In a constrained pseudorandom function (PRF), the master secret key can be
used to derive constrained keys, where each constrained key In this paper we introduce the concept of private constrained PRFs, which
are constrained PRFs with the additional property that a constrained key
does not reveal its constraint. Our main notion of privacy captures the
intuition that an adversary, given a constrained key To construct private constrained PRFs we first demonstrate that our strongest notions of privacy and functionality can be achieved using indistinguishability obfuscation. Then, for our main constructions, we build private constrained PRFs for bit-fixing constraints and for puncturing constraints from concrete algebraic assumptions.
**Paper:**[PDF], [ePrint Version]
BibTeX:
@inproceedings{BLW17, author = {Dan Boneh and Kevin Lewi and David J. Wu}, title = {Constraining Pseudorandom Functions Privately}, booktitle = {International Conference on Practice and Theory in Public-Key Cryptography ({PKC})}, year = {2017} } ## Beyond Software Watermarking: Traitor-Tracing for Pseudorandom Functions
Abstract:
Software watermarking schemes allow a user to embed an identifier into a piece of code such that the resulting program is nearly functionally-equivalent to the original program, and yet, it is difficult to remove the identifier without destroying the functionality of the program. Such schemes are often considered for proving software ownership or for digital rights management. Existing constructions of watermarking have focused primarily on watermarking pseudorandom functions (PRFs). In this work, we revisit the definitional foundations of watermarking, and
begin by highlighting a major flaw in existing security notions. Existing
security notions for watermarking only require that the identifier be
successfully extracted from programs that preserve the To address the shortcomings in existing watermarkable PRF definitions, we
introduce a new primitive called a
**Paper:**[PDF], [ePrint Version]
BibTeX:
@inproceedings{GKWW21, author = {Rishab Goyal and Sam Kim and Brent Waters and David J. Wu}, title = {Beyond Software Watermarking: Traitor-Tracing for Pseudorandom Functions}, booktitle = {{ASIACRYPT}}, year = {2021} } ## Watermarking Cryptographic Functionalities from Standard Lattice Assumptions
Abstract:
A software watermarking scheme allows one to embed a “mark” into a program without significantly altering the behavior of the program. Moreover, it should be difficult to remove the watermark without destroying the functionality of the program. Recently, Cohen et al. (STOC 2016) and Boneh et al. (PKC 2017) showed how to watermark cryptographic functions such as PRFs using the full power of general-purpose indistinguishability obfuscation. Notably, in their constructions, the watermark remains intact even against arbitrary removal strategies. A natural question is whether we can build watermarking schemes from standard assumptions that achieve this strong mark-unremovability property. We give the first construction of a watermarkable family of PRFs that satisfy this strong mark-unremovability property from standard lattice assumptions (namely, the learning with errors (LWE) and the one-dimensional short integer solution (SIS) problems). As part of our construction, we introduce a new cryptographic primitive called a translucent PRF. Next, we give a concrete construction of a translucent PRF family from standard lattice assumptions. Finally, we show that using our new lattice-based translucent PRFs, we obtain the first watermarkable family of PRFs with strong unremovability against arbitrary strategies from standard assumptions.
**Paper:**[PDF], [Journal Version], [ePrint Version]
BibTeX (Conference):
@inproceedings{KW17, author = {Sam Kim and David J. Wu}, title = {Watermarking Cryptographic Functionalities from Standard Lattice Assumptions}, booktitle = {{CRYPTO}}, year = {2017} } BibTeX (Journal):
@article{KW21, author = {Sam Kim and David J. Wu}, title = {Watermarking Cryptographic Functionalities from Standard Lattice Assumptions}, journal = {J. Cryptology}, volume = {34}, number = {28}, pages = {1--76}, year = {2021} } ## Constrained Keys for Invertible Pseudorandom FunctionsAbstract:
A constrained pseudorandom function (PRF) is a secure PRF for which one can
generate constrained keys that can only be used to evaluate the PRF on a
subset of the domain. Constrained PRFs are used widely, most notably in
applications of indistinguishability obfuscation (iO). In this paper we show
how to constrain an invertible PRF (IPF), which is significantly harder. An
IPF is a secure injective PRF accompanied by an inversion algorithm. A
constrained key for an IPF can only be used to evaluate the IPF on a subset
**Paper:**[PDF], [ePrint Version]**Talk:**[Slides]
BibTeX:
@inproceedings{BKW17, author = {Dan Boneh and Sam Kim and David J. Wu}, title = {Constrained Keys For Invertible Pseudorandom Functions}, booktitle = {{TCC}}, year = {2017} } |