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

namespace AES
{
    class Program
    {
        public static byte[] salt;
        public static byte[] saltBytes;

        static void Main(string[] args)
        {
            var a = "Hello";
            var bytes = Encoding.ASCII.GetBytes(a);

            var secure = new Program();

            var encrypted = secure.EncryptText("abc", "123");

            Console.WriteLine(encrypted);

            Console.WriteLine(secure.DecryptText(encrypted, "123"));
        }

        public string EncryptText(string input, string password)
        {
            // Get the bytes of the string
            byte[] bytesToBeEncrypted = Encoding.UTF8.GetBytes(input);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(password);

            // Hash the password with SHA256
            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

            byte[] bytesEncrypted = AES_Encrypt(bytesToBeEncrypted, passwordBytes);

            string result = Convert.ToBase64String(bytesEncrypted);

            return result;
        }

        public string DecryptText(string input, string password)
        {
            // Get the bytes of the string
            byte[] bytesToBeDecrypted = Convert.FromBase64String(input);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

            byte[] bytesDecrypted = AES_Decrypt(bytesToBeDecrypted, passwordBytes);

            string result = Encoding.UTF8.GetString(bytesDecrypted);

            return result;
        }

        public byte[] AES_Encrypt(byte[] bytesToBeEncrypted, byte[] passwordBytes)
        {
            byte[] encryptedBytes = null;

            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.

            new RNGCryptoServiceProvider().GetBytes(salt = new byte[32]);
            saltBytes = salt;

            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {

                    AES.KeySize = 256;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    var iv = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.IV = iv.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeEncrypted, 0, bytesToBeEncrypted.Length);
                        cs.Close();
                    }
                    encryptedBytes = ms.ToArray();
                }
            }

            return encryptedBytes;
        }

        public byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {

            byte[] decryptedBytes = null;

            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.

            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    var iv = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.IV = iv.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                        cs.Close();
                    }
                    decryptedBytes = ms.ToArray();
                }
            }

            return decryptedBytes;
        }

    }
}