Fair Computation with Tit-for-Tat Strategy

Complete fairness means that either all parties learn the output of the function or none of them does. It was deemed as an impossible task in general in secure two party computation by Cleve (STOC 1986). However, a seminal result of complete fairness between two parties was achieved by Gordorn et al. (STOC 2008). Recently Groce and Katz (Euro crypt 2012) corrected the insufficient assumptions and gave some positive results of fairness. Here we revisit this problem and introduce the Tit-for-Tat (TFT) strategy into rational two-party computation. To the best of our knowledge, it is the first secure two-party computation protocol with constant rounds that allows both parties to know the terminal round.