[Resource Topic] 1998/019: Many-to-one Trapdoor Functions and their Relation to Public-key Cryptosystems

Welcome to the resource topic for 1998/019

Title:
Many-to-one Trapdoor Functions and their Relation to Public-key Cryptosystems

Authors: Mihir Bellare, Shai Halevi, Amit Sahai, Salil Vadhan

Abstract:

The heart of the task of building public key cryptosystems is viewed
as that of making trapdoors;'' in fact, public key cryptosystems and trapdoor functions are often discussed as synonymous. How accurate is this view? In this paper we endeavor to get a better understanding of the nature of trapdoorness’’ and its relation to public key
cryptosystems, by broadening the scope of the investigation: we look
at general trapdoor functions; that is, functions that are not
necessarily injective (ie., one-to-one). Our first result is somewhat
surprising: we show that non-injective trapdoor functions (with
super-polynomial pre-image size) can be constructed {from} any one-way
function (and hence it is unlikely that they suffice for public key
encryption). On the other hand, we show that trapdoor functions with
polynomial pre-image size are sufficient for public key encryption.
Together, these two results indicate that the pre-image size is a
fundamental parameter of trapdoor functions. We then turn our
attention to the converse, asking what kinds of trapdoor functions can
be constructed from public key cryptosystems. We take a first step by
showing that in the random-oracle model one can construct injective
trapdoor functions from any public key cryptosystem.

ePrint: https://eprint.iacr.org/1998/019

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