AESencrypt/Program.cs

// See https://aka.ms/new-console-template for more information
using ConfigurationManager = System.Configuration.ConfigurationManager;
using System.Collections.Specialized;
using System.Security.Cryptography;
using System.Text;

namespace aesencrypt;

public class Program
{
    static void encrypt(string plainText, string encryptionKey)
    {
        byte[] keyBytes = Encoding.UTF8.GetBytes(encryptionKey);

        using (Aes aes = Aes.Create())
        {
            aes.Key = keyBytes;
            aes.GenerateIV(); // Always generate a new IV

            using (var encryptor = aes.CreateEncryptor(aes.Key, aes.IV))
            {
                byte[] plainBytes = Encoding.UTF8.GetBytes(plainText);
                byte[] encryptedBytes = encryptor.TransformFinalBlock(plainBytes, 0, plainBytes.Length);

                // Combine IV and encrypted data
                byte[] combinedBytes = new byte[aes.IV.Length + encryptedBytes.Length];
                Buffer.BlockCopy(aes.IV, 0, combinedBytes, 0, aes.IV.Length);
                Buffer.BlockCopy(encryptedBytes, 0, combinedBytes, aes.IV.Length, encryptedBytes.Length);

                Console.WriteLine(Convert.ToBase64String(combinedBytes));
            }
        }
    }

    static void decrypt(string plainText,string encryptionKey)
        {
            byte[] fullCipher = Convert.FromBase64String(plainText);
            byte[] iv = new byte[16];
            byte[] cipher = new byte[fullCipher.Length - iv.Length];

            Buffer.BlockCopy(fullCipher, 0, iv, 0, iv.Length);
            Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, cipher.Length);

            byte[] keyBytes = Encoding.UTF8.GetBytes(encryptionKey);

            using (Aes aes = Aes.Create())
            {
                aes.Key = keyBytes;
                aes.IV = iv;

                using (var decryptor = aes.CreateDecryptor(aes.Key, aes.IV))
                {
                    byte[] decryptedBytes = decryptor.TransformFinalBlock(cipher, 0, cipher.Length);
                    Console.WriteLine(Encoding.UTF8.GetString(decryptedBytes));
                }
            }
        }
    
        static void Main(string[] args)
        {
            var  Initialconfiguration = ConfigurationManager.GetSection("settings") as NameValueCollection;
            string function = Initialconfiguration["function"];
            string encryptionKeyUsed = Initialconfiguration["key"];
            if (function == "encrypt")
            {
                Console.WriteLine("What do you want to encrypt?");
                encrypt(Console.ReadLine(),encryptionKeyUsed);
            }
            else if (function == "decrypt")
            {
                Console.WriteLine("What do you want to decrypt?");
                decrypt(Console.ReadLine(),encryptionKeyUsed);
            }
            else
            {
                Console.WriteLine("Invalid function type");
            }

            Console.ReadLine();

        }

}