How to Encrypt and Decrypt a string in C#  

Here is a code snippet to help you encrypt and decrypt a string in C#.

The key is hardcoded, but in your own project you may want to read it from a secure store, or perhaps a config file or environment variable.

Notice that the key is being hashed for an extra layer of security.

using System;
using System.Security.Cryptography;
using System.Text;

namespace Crypto
{
    class Program
    {
        static string key { get; set; } = "A!9HHhi%XjjYY4YP2@Nob009X";

        static void Main(string[] args)
        {
            var text = "This is a test string";
            Console.WriteLine(text);

            var cipher = Encrypt(text);
            Console.WriteLine(cipher);

            text = Decrypt(cipher);
            Console.WriteLine(text);

            Console.ReadKey();
        }

        public static string Encrypt(string text)
        {
            using (var md5 = new MD5CryptoServiceProvider())
            {
                using (var tdes = new TripleDESCryptoServiceProvider())
                {
                    tdes.Key = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                    tdes.Mode = CipherMode.ECB;
                    tdes.Padding = PaddingMode.PKCS7;

                    using (var transform = tdes.CreateEncryptor())
                    {
                        byte[] textBytes = UTF8Encoding.UTF8.GetBytes(text);
                        byte[] bytes = transform.TransformFinalBlock(textBytes, 0, textBytes.Length);
                        return Convert.ToBase64String(bytes, 0, bytes.Length);
                    }
                }
            }
        }

        public static string Decrypt(string cipher)
        {
            using (var md5 = new MD5CryptoServiceProvider())
            {
                using (var tdes = new TripleDESCryptoServiceProvider())
                {
                    tdes.Key = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                    tdes.Mode = CipherMode.ECB;
                    tdes.Padding = PaddingMode.PKCS7;

                    using (var transform = tdes.CreateDecryptor())
                    {
                        byte[] cipherBytes = Convert.FromBase64String(cipher);
                        byte[] bytes = transform.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);
                        return UTF8Encoding.UTF8.GetString(bytes);
                    }
                }
            }
        }
    }
}

And here is the output:

This is a test string

S6HLAUmPMGBPKVT5qVbyuFNQhMTA9/UY

This is a test string