This technique is described in the paper: 2.4 The Start Out As Friends Protocol The Start Out As Friends Protocol (SOAP), as presented by [9], is summarized in

This technique is described in the paper: 2.4 The Start Out As Friends Protocol The Start Out As Friends Protocol (SOAP), as presented by [9], is summarized in Figure 1. In this protocol, Alice and Bob participate in many exchanges over a long period, transferring pieces of information that provide only incremental evidence of their responses. Over time, each party can become more and more confident in the other’s answer, until the probability of a mismatch is low enough that a JMAP exchange becomes feasible. Unfortunately, the runtime of this protocol may be inordinately long in some cases, and deriving evidence from the individual transmissions can be difficult. There are also highly complex failure modes when dealing with a malicious adversary, as Munroe illustrates in his paper. [9] R. Munroe. Friends. May 2008. https://xkcd.com/513/ https://xkcd.com/513/