Oracle Separation in the Non-uniform Model

Abstract. Oracle separation methods are used in cryptography to rule out blackbox reductions between cryptographic primitives. It is sufficient to find an oracle relative to which the base primitive exists but there are no secure instances of the constructed primitive. In practice, it is beyond our current reach to construct a fixed oracle with such properties for most of the reductions because it is difficult to guarantee the existence of secure base primitives. For example, to show that there exist no black-box reductions from collision-free functions to one-way permutations we have to show that secure one-way permutations exist relative to the oracle. However, no deterministic constructions for unconditionally secure one-way permutations are known yet. To overcome this gap, randomized oracles are used to create random base primitives that are secure on average. After that, a fixed oracle with the desired properties is extracted from the probability distribution by using non-con...

• Type: Conference
• Year: 2009
• Where: PROVSEC
• Authors: Ahto Buldas, Sven Laur, Margus Niitsoo
• Keywords: Black-box Reductions, Oracle, PROVSEC 2009, Reductions