With the HelloSign Ruby SDK by HelloSign and Derek Barncard, developers can interact with the API features of electronic signature. Resources include installation and configuration. To test callbacks against a local server, users can work with a tunneling service such as ngrok available at http://ngrok.com
The Signinghub API helps accomplish something that looks simple (see image below) but is tricky to do securely: digitally sign a document. The API, using REST-based web services with XML responses, makes its possible to incorporate digital signing into your application that is based on the Public Key Infrastructure.