On the lossiness of the rabin trapdoor function

Abstract

Lossy trapdoor functions, introduced by Peikert and Waters (STOC '08), are functions that can be generated in two indistinguishable ways: either the function is injective, and there is a trapdoor to invert it, or the function is lossy, meaning that the size of its range is strictly smaller than the size of its domain. Kakvi and Kiltz (EUROCRYPT 2012) proved that the Full Domain Hash signature scheme based on a lossy trapdoor function has a tight security reduction from the lossiness of the trapdoor function. Since Kiltz, O'Neill, and Smith (CRYPTO 2010) showed that the RSA trapdoor function is lossy under the -Hiding assumption of Cachin, Micali, and Stadler (EUROCRYPT '99), this implies that the RSA Full Domain Hash signature scheme has a tight security reduction from the Φ-Hiding assumption (for public exponents e