Actively Secure Two-Party Computation: Ecient

Himanshu Tyagi, Shun Watanabe

Jesper Buus Nielsen, Peter Sebastian Nordholt, Claudio Orlandi +1 more

Pille Pullonen

Renren Dong

Liqun Chen

We propose a new ecient protocol, which allows a pair of potentially mistrusting parties to exchange digital signatures over the Internet in a fair way, such that after the protocol is running, either each party obtains the other's signature, or neither of them does. The pro- tocol relies on an o-line Trusted Third Party (TTP), which does not take part in the exchange unless any of the parties behaves improperly or other faults occur. Eciency of the protocol is achieved by using a cryptographic primitive, called conrmable signatures (or designated con- rmer signatures in its original proposal (9)). We recommend using a new ecient conrmable signature scheme in the proposed fair exchange pro- tocol. This scheme combines the family of discrete logarithm (DL) based signature algorithms and a zero-knowledge (ZK) proof on the equality of two DLs. The protocol has a practical level of performance: only a moderate number of communication rounds and ordinary signatures are required. The security of the protocol can be established from that of the underlying signature algorithms and that of the ZK proof used.

Chih-Hao Shen, Justin Z. Zhan, Tsan‐sheng Hsu +2 more

Secure multiparty computation is a very important research topic in cryptography. The sub-problem of secure multiparty computation that has received special attention by researchers because of its close relation to many cryptographic tasks is secure two-party computation. This area of research is concerned with the question: ldquoCan two party computation be achieved more efficiently and under weaker security assumptions than general multiparty computation?rdquo Yaopsilas protocol provided security against passive adversaries, while Lindell and Pinkas proposed secure two party protocols that are secure against active adversaries. In this paper, we would like to propose a set of information theoretically secure protocols based on scalar product protocol. The detailed complexity analysis is also provided.