How to encrypt calls with SIP encryption?

• Run the SimpleCA with the SimpleCA.exe file. First, you need to set up a root CA:
  

  

• In the Server Certificates menu choose New Server Certificate Request:
  

  

• Within the following form you have to provide some information. Please not that, within the Common Name field you have to provide the domain name or IP address of the PBX, where you can reach it:
  

  

  
  Click on the OK button, than give a name for the Certificate Signing Request, and click on the Save button.
• Now you have an unsigned Server Certificate Request, you just have to sign it. In the Server Certificates menu choose Sign Server Certificate Request and select the previously created .csr file:
  

  

  
  Check the given data and click on the OK button.
• Finally, you will be asked asked about the CA Key Password (which you were set at the starting of SimpleCA):
  

  

  
  Type in the password, and Simple CA will generate three files into the certificates directory. With the help of these files, you need to set the TLS certification within your preferred PBX.

• From the simpleca directory, run the ca.crt file:
  

  

• Within the General tab, click on the Install Certificate... button:
  

  

  
  than the Next button.
• Choose the Place all certificates in the following store option, and clik on the Browse button:
  

  

• Select the Trusted Root Certification Authorities:
  

  

  than click the OK, the Next, and the Finish button.
• You will receive a warning message via the Security Warning window as a warning about the certification's installation, and asks you if you really want to install it or not. Click on the Yes button, and you are ready to set the TLS encryption within your softphone (as the following example source code introduces).

using System;
using Ozeki.Network;
using Ozeki.VoIP;

namespace SIP_Encryption
{
    class Program
    {
        static ISoftPhone softphone;
        static IPhoneLine phoneLine;

        private static void Main(string[] args)
        {
            // Create a softphone object with RTP port range 5000-10000
            softphone = SoftPhoneFactory.CreateSoftPhone(5000, 10000);

            // SIP account registration data, (supplied by your VoIP service provider)
            var registrationRequired = true;
            var userName = "sipusername";
            var displayName = "sipdisplayname";
            var authenticationId = "authenticationid";
            var registerPassword = "Password";
            var domainHost = "pbxip.voipprovider.com";
            var domainPort = 5060;

            var account = new SIPAccount(registrationRequired, displayName, userName, authenticationId, registerPassword, domainHost, domainPort);

            // Send SIP regitration request
            RegisterAccount(account);

            // Prevents the termination of the application
            Console.ReadLine();
        }


        static void RegisterAccount(SIPAccount account)
        {
            try
            {
                var phoneLineConfig = new PhoneLineConfiguration(account);
                phoneLineConfig.TransportType = TransportType.Tls;
                phoneLine = softphone.CreatePhoneLine(phoneLineConfig);
                phoneLine.RegistrationStateChanged += line_RegStateChanged;
                softphone.RegisterPhoneLine(phoneLine);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error during SIP registration: " + ex.ToString());
            }
        }

        static void line_RegStateChanged(object sender, RegistrationStateChangedArgs e)
        {
            if (e.State == RegState.NotRegistered || e.State == RegState.Error)
                Console.WriteLine("Registration failed!");

            if (e.State == RegState.RegistrationSucceeded)
                Console.WriteLine("Registration succeeded - Online!");
        }
    }
}