July 27, 2023, 12:30 p.m. |

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ePrint Report: New Random Oracle Instantiations from Extremely Lossy Functions

Chris Brzuska, Geoffroy Couteau, Christoph Egger, Pihla Karanko, Pierre Meyer


We instantiate two random oracle (RO) transformations using Zhandry's extremely lossy function (ELF) technique (Crypto'16).


Firstly, using ELFs and indistinguishabililty obfuscation (iO), we instantiate a modified version of the Fujisaki-Okamoto (FO) transform which upgrades a public-key encryption scheme (PKE) from indistinguishability under chosen plaintext attacks (IND-CPA) to indistinguishability under chosen ciphertext attacks (IND-CCA). We side-step a prior uninstantiability result for …

chris crypto elf eprint report function functions lossy obfuscation oracle random report version

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