Get Started with Number Masking Using Go

    Overview

    Phone number masking hides the phone numbers of parties in a call from each other. Many businesses find it advantageous to anonymize communication between two parties — for example, between a customer and a delivery agent on a food delivery service platform or a driver and a rider using a ride-hailing application. Businesses can implement phone number masking by sending calls through an intermediate phone number that acts as a proxy between the two parties. A Plivo number can serve as the intermediate number to connect the two parties while keeping their contact information private.

    How it works

    Implementation

    As an example, we’ll build a number-masking application for a food delivery service that lets the company connect customers with delivery agents and vice versa without revealing any actual phone numbers. To do this, you

    1. Create a customer-to-agent phone number mapping in your application’s back end.
    2. Create the number masking application using Plivo.
    3. Assign the number masking application to a Plivo number.

    In this section, we’ll walk through how to set up a Go server in five minutes and start handling incoming calls. First, download and install Go if necessary.

    Install the Plivo Go SDK

    To install the Plivo Go SDK, create a project directory with the command mkdir mygoapp and change to it with the command cd mygoapp. Then install the Plivo Go package using the go command:

      $ go get github.com/plivo/plivo-go
    

    You can also install the SDK by cloning our GitHub repository into your GOPATH.

    Create a 1:1 map with actual numbers

    Now create customer-to-agent phone number mapping for the application. Whenever a customer places an order, their phone number should be stored in a database for your application to access. A delivery agent will be assigned for the order, and the agent’s number will also be stored in your database, and will be mapped to the customer’s number:

    Customer’s Number		<->		Agent’s Number
      1-415-666-7777					1-415-666-7778
    

    We created sample mapping data in a .env file:

    json
    BASEMAP = {"14156667777":"14156667778","14156667779":"14156667780","14156667781":"14156667782"}
    

    Create a Go server for number masking

    Create a file (we called ours masking.go) and paste into it this code.

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    package main
    
    import (
    	"encoding/json"
    	"log"
    	"os"
    
    	"github.com/gin-gonic/gin"
    	"github.com/joho/godotenv"
    	"github.com/plivo/plivo-go/xml"
    )
    
    // init gets called before the main function
    func init() {
    	// Log error if .env file does not exist'
    	err := godotenv.Load(".env")
    	if err != nil {
    		log.Fatal("Error loading .env file")
    	}
    }
    
    // Handle incoming calls to a Plivo number, connect agent with customer and vice versa without revealing their actual phone numbers.
    func main() {
    	r := gin.Default()
    	r.GET("/number_masking", func(c *gin.Context) {
    		customerAgentmap := os.Getenv("BASEMAP")
    		// Declares an empty map interface
    		var result map[string]string
    		fromNumber := c.Query("From")
    		toNumber := c.Query("To")
    		// Unmarshal or Decode the JSON to the interface.
    		json.Unmarshal([]byte(customerAgentmap), &result)
    		agentCustomermap := reverseMap(result)
    		_, custToagent := result[fromNumber]
    		_, agenTocust := agentCustomermap[fromNumber]
    		if custToagent { // To check if the Customer's number is existing in the Customer-Agent mapping
    			destNumber := result[fromNumber] // This will assign the Value from the customer-agent array to number variable
    			c.XML(200, xml.ResponseElement{
    				Contents: []interface{}{
    					new(xml.DialElement).
    						SetCallerID(toNumber). // Plivo number will be used as the caller ID for the call towards Agent
    						SetContents([]interface{}{
    							new(xml.NumberElement).
    								SetContents(destNumber),
    						}),
    				},
    			})
    		} else if agenTocust { // To check if the Agent's number is existing in the Customer-Agent mapping
    			destNumber := agentCustomermap[fromNumber] // This will assign the Key from the customer-agent array to number variable
    			c.XML(200, xml.ResponseElement{
    				Contents: []interface{}{
    					new(xml.DialElement).
    						SetCallerID(toNumber). // Plivo number will be used as the caller ID for the call towards Customer
    						SetContents([]interface{}{
    							new(xml.NumberElement).
    								SetContents(destNumber),
    						}),
    				},
    			})
    		}
    		c.Header("Content-Type", "application/xml")
    	})
    	r.Run() // listen and serve on 0.0.0.0:8080 (for windows "localhost:8080")
    }
    
    // Reverse the Basemap from env file to get Customer <> Agent Mapping data
    func reverseMap(m map[string]string) map[string]string {
    	n := make(map[string]string)
    	for k, v := range m {
    		n[v] = k
    	}
    	return n
    }
    

    To run this file on the server, go to the folder where the file resides and use the command

    $ go run masking.go
    

    You should see your basic server app in action on http://localhost:8080/number_masking/

    Expose your local server to the internet

    To receive incoming calls, your local server should be able to connect with Plivo API services. For that, we recommend using ngrok, which exposes local servers behind NATs and firewalls to the public internet over secure tunnels.

    ngrok block diagram

    Install ngrok and run it on the command line, specifying the port that hosts the application on which you want to receive messages (8080 in this case):

    ./ngrok http 8080
    

    Ngrok will display a forwarding link that you can use as a webhook to access your local server over the public network.

    Sample ngrok CLI

    Now people can call your Plivo number. If an incoming call to your Plivo number is from one of the customer phone numbers in the Customer <-> Agent Map — for example, if the caller number is 14156667777 — then Plivo will send the XML response to process the incoming call as below, and you can check the XML document in your browser.

    XML Document - Customer Calls Agent

    If the incoming call to your Plivo number is from one of the agent phone numbers in the Customer <-> Agent Map — for example, if the caller number is 14156667778 — then Plivo will send the XML response to process the incoming call as below, and you can check the XML document in your browser.

    XML Document - Agent Calls Customer

    Create a Plivo application

    1. Create a Plivo application by visiting the Voice > Applications > XML page of the console and clicking on Add New Application, or by using Plivo’s Application API.

    2. Give your application a name — we used Number Masking. Enter your server URL (for example, https://61d8fb8f250c.ngrok.io/handleincoming/) in the Primary Answer URL field and set the method as GET. See our Application API docs to learn how to modify your application through our APIs.

    3. Click on Create Application to save your application.

    Create Application — Number Masking

    Assign a Plivo number to your application

    1. Navigate to the Numbers page and select the phone number you want to use for the application.
    2. Select XML Application from the Application Type drop-down list, and Number Masking (the name of the application) from the Plivo Application drop-down list.
    3. Click on Update Number to save the number assignment.

      Assign Application - Number Masking

    Test and validate

    To test the application, you need two Plivo mobile numbers. Set up one of your mobile numbers as a customer and another as an agent in the customer-to-agent mapping data in the config file. Make a call from each of your mobile numbers to the Plivo number you mapped to the application. You should see that the call is forwarded to the other number, and the incoming call has the Plivo number as the caller ID.