MIDI decryption algorithm for Magic Tiles 3

Program.cs

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

namespace mt3decrypt
{
    class Program
    {
        static readonly string MIDIKey = "$jshHgdn123&Am@n0te3+x";

        static void Main(string[] args)
        {
            var key = Encoding.UTF8.GetBytes(MIDIKey);
            var sha256 = SHA256.Create();
            var key_hash = sha256.ComputeHash(key);

            var salt = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };
            var derive = new Rfc2898DeriveBytes(key_hash, salt, 1000);

            var aes = new RijndaelManaged();
            aes.KeySize = 256;
            aes.BlockSize = 128;
            aes.Key = derive.GetBytes(32);
            aes.IV = derive.GetBytes(16);
            aes.Mode = CipherMode.CBC;
            var dec = aes.CreateDecryptor();

            var input = File.ReadAllBytes("D:\\Someoneleaving.mid.encrypted");
            var output = new byte[input.Length];

            using (MemoryStream ms = new MemoryStream(input))
            {
                using (CryptoStream cs = new CryptoStream(ms, dec, CryptoStreamMode.Read))
                {
                    cs.Read(output);
                }
            }

            File.WriteAllBytes("D:\\Someoneleaving.mid", output);
        }
    }
}