A constrained pseudorandom function (CPRF) F: K×X → Y for a family T of subsets of χ is a function where for any key k ∈ K and set S ∈ T one can efficiently compute a short constrained key kS, which allows to evaluate F(k, ·) on all inputs x ∈ S, while the outputs on all inputs x /∈ S look random even given kS. Abusalah et al. recently constructed the first constrained PRF for inputs of arbitrary length whose sets S are decided by Turing machines. They use their CPRF to build broadcast encryption and the first ID-based non-interactive key exchange for an unbounded number of users. Their constrained keys are obfuscated circuits and are therefore large. In this work we drastically reduce the key size and define a constrained key for a Turing machine M as a short signature on M. For this, we introduce a new signature primitive with constrained signing keys that let one only sign certain messages, while forging a signature on others is hard even when knowing the coins for key generation.
H. Abusalah—Research supported by the European Research Council, ERC starting grant (259668-PSPC) and ERC consolidator grant (682815 - TOCNeT).
445 - 463
ACNS: Applied Cryptography and Network Security
2016-06-19 – 2016-06-22
Abusalah HM, Fuchsbauer G. Constrained PRFs for unbounded inputs with short keys. In: Vol 9696. Springer; 2016:445-463. doi:10.1007/978-3-319-39555-5_24
Abusalah, H. M., & Fuchsbauer, G. (2016). Constrained PRFs for unbounded inputs with short keys (Vol. 9696, pp. 445–463). Presented at the ACNS: Applied Cryptography and Network Security, Guildford, UK: Springer. https://doi.org/10.1007/978-3-319-39555-5_24
Abusalah, Hamza M, and Georg Fuchsbauer. “Constrained PRFs for Unbounded Inputs with Short Keys,” 9696:445–63. Springer, 2016. https://doi.org/10.1007/978-3-319-39555-5_24.
H. M. Abusalah and G. Fuchsbauer, “Constrained PRFs for unbounded inputs with short keys,” presented at the ACNS: Applied Cryptography and Network Security, Guildford, UK, 2016, vol. 9696, pp. 445–463.
Abusalah HM, Fuchsbauer G. 2016. Constrained PRFs for unbounded inputs with short keys. ACNS: Applied Cryptography and Network Security, LNCS, vol. 9696, 445–463.
Abusalah, Hamza M., and Georg Fuchsbauer. Constrained PRFs for Unbounded Inputs with Short Keys. Vol. 9696, Springer, 2016, pp. 445–63, doi:10.1007/978-3-319-39555-5_24.
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