Notions of Reducibility between Cryptographic Primitives

Starting with the seminal paper of Impagliazzo and Rudich [17], there has been a large body of work showing that various cryptographic primitives cannot be reduced to each other via “black-box” reductions. The common interpretation of these results is that there are inherent limitations in using a primitive as a black box, and that these impossibility results can be overcome only by explicitly using the code of the primitive in the construction.In this paper we revisit these negative results, give a more careful taxonomy of the ways in which “black-box reductions” can be formalized, strengthen some previous results (in particular giving unconditional impossibility results for reductions that were previously only shown to imply P≠ NP), and offer a new interpretation of them: in many cases, there is no limitation in using a primitive as a black box, but there is a limitation in treating adversaries as such. In particular, these negative results may be overcome by using the code of the adversary in the analysis.