IntroductionThis is a rigorous do-it-from-scratch article series where I cover how to implement a multiparty (of two) signing process. This technique allows two people, each contributing with his part, to build a joint signature. This application has several use cases. For instance, one person could split a private key into two shares and store each share in a different device, which diminishes the risk of having his private key compromised. Also, now it would be possible for two people to pa...