Cryptolens 

An API documentation can be found at http://api.serialkeymanager.com/. This is a client API that serves as an interface to SKM Web API (app.cryptolens.io/docs/api/). NB: There is also one for C++ (https://github.com/SerialKeyManager/SKM-Client-API-CPP)

An API documentation can be found at https://help.cryptolens.io/api/dotnet/. This is a client API that serves as an interface to Cryptolens Web API (app.cryptolens.io/docs/api/). NB: There is also one for C++ (https://github.com/Cryptolens/cryptolens-cpp)

This library helps you to 1) verify a VAT number using the European Commission's API and 2) get the tax percentage (VAT) that should be applied to an invoice. The package is aimed at European businesses (i.e. companies within the EU).

Implements two-factor authentication support (both time and counter based).