Code implementing a simple payment protocol for Bitcoin (PaymentRequest/etc). See https://en.bitcoin.it/wiki/BIP_0070 Files here: paymentrequest.proto : Google protocol buffer definition of messages Subdirectories here: c++ : command-line utilities for creating/validating PaymentRequests php : php code and a demo website for creating/validating PaymentRequests ca_in_a_box : "certificate authority in a box", used to generate certificates and certificate chains for testing.