Build a custom Credential Provider

As part of a bigger solution, we need a custom credential provider, that would allow a user to log on to a standard environment with a single button click. The environments that should be made available using buttons, will be stored in an encrypted XML file. An example is included, as well as an example c# project that makes such a file. The encryption will be PGP with a standard, hard-coded pass-phrase. You will build the credential provider using c++, using Visual Studio. The Credential Provider should function in Windows 7, 8, 8.1 and Windows 10 on 32-bit and 64-bit platforms. An installer is not required. Attached are detailed specifications and examples. Please read these specifications before placing a bid.