Cryptoprotocols: Subscription to a Public Key, The Secret Blocking and The Multi-Player Mental Poker Game (extended abstract)

Abstract

Investigating the capabilities of public key and related cryptographic techniques has recently become an important area of cryptographic research. In this paper we present some new algorithms and cryptographic protocols (Cryptoprotocols) which enlarge the range of applications of public key systems and enable us to perform certain transactions in communication networks. The basic cryptographic tools used are Rabin’s Oblivious Transfer Protocol and an algorithm we developed for Number Embedding which is provably hard to invert. We introduce the protocol Subscription to a Public Key, which gives a way to transfer keys over insecure communication channels and has useful applications to cryptosystems. We develop the Secret Blocking Protocol, specified as follows: ‘A transfers a secret to B, B can block the message. If B does not block it, there is a probability P that he might get it. (1/2 ≤ P < 1, where we can control the size of P). A does not know if the message was blocked (but he can find out later)’. The classic cryptotransaction is the Mental Poker Game. A cryptographically secure solution to the Multi Player Mental Poker Game is given. The approach used in constructing the solution provides a general methodology of provable and modular Protocol Composition.