C# Encryption v2

Encryption Class

Create a new Encryption.cs file and paste in the following c# code.

/* .NET Core SDK version 2.2
 * https://docs.microsoft.com/en-us/dotnet/core/tutorials/with-visual-studio-code
 */
using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

class Encryption
{
    public string ivKey;
    public string secretKey;
	
    public Encryption (string ivKey, string secretKey) {
        this.ivKey = ivKey;
        this.secretKey = secretKey;
    }

 private string HashString(string str)
    	{
    		var stringBuilder = new StringBuilder();
    		using (var hash = SHA256.Create())
    		{
    			var result = hash.ComputeHash(Encoding.UTF8.GetBytes(str));
    			foreach (var x in result)
    			{
    				stringBuilder.Append(x.ToString("x2"));
    			}
    		}
    
    		return stringBuilder.ToString();
    	}
	
	public string Encrypt(string payload)
        {

            byte[] encrypted;

            using (AesCryptoServiceProvider aes = new AesCryptoServiceProvider())
            {
                aes.KeySize = 256;
                aes.BlockSize = 128;
                aes.Key = Encoding.UTF8.GetBytes(HashString(this._ivKey).Substring(0, 16));
                aes.IV = Encoding.UTF8.GetBytes(HashString(this._secretKey).Substring(0, 16));
                aes.Mode = CipherMode.CBC;
                aes.Padding = PaddingMode.PKCS7;

                ICryptoTransform enc = aes.CreateEncryptor(aes.Key, aes.IV);

                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, enc, CryptoStreamMode.Write))
                    {
                        using (StreamWriter sw = new StreamWriter(cs))
                        {
                            sw.Write(payload);
                        }

                        encrypted = ms.ToArray();
                    }
                }
            }
            return Convert.ToBase64String(Encoding.UTF8.GetBytes(Convert.ToBase64String(encrypted)));
        }
}

Encryption Class Usage (.NET)

For this example, we will use .NET to give a realistic example. Use the examples below to setup this C# demo if you do not have a .NET application already. A more comprehensive guide can be found here.

Step 1: Create a project directory $ mkdir checkout-demo

Step 2: Go into the project directory $ cd checkout-demo

Step 3: Generate a new project following the Web API template $ dotnet new webapi

Then create a file CheckoutController.cs and paste in the code below. Open a terminal session in your project directory and run the application using the command dotnet run

using System;
using Checkout.Models;
using CheckoutEncryption.utils;
using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json;

namespace CheckoutEncryption.Controllers
{
    public class CheckoutController : Controller
    {
        [HttpPost("checkout-encryption")]
        public ActionResult CheckoutEncryption([FromBody] Payload payload)
        {
            string accessKey = "";
            string ivKey = "";
            string secretKey = "";

            Encryption encryption = new Encryption(ivKey, secretKey);
            
            string json = JsonConvert.SerializeObject(payload).Replace("/", "\\/");
            Console.WriteLine(json);

            string encParams = encryption.Encrypt(json);

            return Json(new {param = encParams, accessKey = accessKey, countryCode = payload.countryCode});
        }
    }
}
    
    
// Payload Model
public class Payload
{
    public string merchantTransactionID { get; set; }

    public string customerFirstName { get; set; }

    public string customerLastName { get; set; }

    public string MSISDN { get; set; }

    public string customerEmail { get; set; }

    public string requestAmount { get; set; }

    public string currencyCode { get; set; }

    public string accountNumber { get; set; }

    public string serviceCode { get; set; }

    public string dueDate { get; set; }

    public string requestDescription { get; set; }

    public string countryCode { get; set; }

    public string languageCode { get; set; }

    public string successRedirectUrl { get; set; }

    public string failRedirectUrl { get; set; }

    public string paymentWebhookUrl { get; set; }
    
}