Simple Watermarking Pseudorandom Functions from Extractable Pseudorandom Generators
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Abstract
Watermarking pseudorandom functions (PRF) allow an authority to embed an unforgeable and unremovable watermark into a PRF while preserving its functionality. In this work, we extend the work of Kim and Wu [Crypto'19] who gave a simple two-step construction of watermarking PRFs from a class of extractable PRFs satisfying several other properties – first construct a mark-embedding scheme, and then upgrade it to a message-embedding scheme.
While the message-embedding scheme of Kim and Wu is based on complex homomorphic evaluation techniques, we observe that much simpler constructions can be obtained and from a wider range of assumptions, if we forego the strong requirement of security against the watermarking authority. Concretely, we introduce a new notion called extractable PRGs (xPRGs), from which extractable PRFs (without security against authorities) suitable for the Kim-Wu transformations can be simply obtained via the Goldreich-Goldwasser-Micali (GGM) construction. We provide simple constructions of xPRGs from a wide range of assumptions such as hardness of computational Diffie-Hellman (CDH) in the random oracle model, as well as LWE and RSA in the standard model.
References
How to cite
Estuardo Alpirez Bock, Chris Brzuska, and Russell W. F. Lai, "Simple Watermarking Pseudorandom Functions from Extractable Pseudorandom Generators," IACR Communications in Cryptology, vol. 1, no. 2, Jul 08, 2024, doi: 10.62056/aevur-10k.
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