Cybersource is an online credit card payment system that manages fraud and security issues. CyberSource Apple Pay SDK's guide shows how to work with iOS SDK for Apple Pay, methods, objects, properties, and sample code. The actual SDK file name is CyberSourceiOSSDK can be downloaded from Cybersource site.
The W3C Web Payments Working Group has published working drafts of Web Payments HTTP Specifications that include the Web Payments HTTP API 1.0 and Web Payments HTTP Messages 1.0. The two specifications are designed to work together to enable payment requests outside of a browser context.