Computational Oblivious Transfer and Interactive Hashing
We present a simple approach for constructing oblivious transfer (OT) using a trapdoor function (TDF) and interactive hashing (IH). In a nutshell, an OT-receiver inputs a (randomly chosen) function index (encoded as a binary string) into IH. The resulting output strings are interpreted by an OT-sender and used to encrypt his private inputs. Two functions are shown to be eligible: 1) A specific candidate function: a coding based McEliece PKC; 2) A collection of TDF with some special properties, loosely speaking: succinctly representable index set and a unique trapdoor for each index. The aim of this presentation is to show a proof of concept in two ways: 1) Introduction of an apparent connection between OT and IH; 2) Emphasizing importance of IH as a cryptographic primitive in its own right and bringing up some aspects in which the further development of IH may be required.
Information-Theoretic Conditions for Two-Party Secure Function Evaluation
The standard security definition of unconditional secure function evaluation, which is based on the ideal/real model paradigm, has the disadvantage of being overly complicated to work with in practice. On the other hand, simpler ad-hoc definitions tailored to special scenarios have often been flawed. Motivated by this unsatisfactory situation, we give an information-theoretic security definition of secure function evaluation which is very simple yet provably equivalent to the standard, simulation-based definitions.