AES256 Implementation

I coded a little implementation to encrypt and decrypt bytes with AES256 (ECB) in C#. I wanted to know if I can optimize/cleanup my code a bit more, or if it i fine like this:

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

namespace AES256
{
class Program
{

private static string getString(byte[] b)
{
return Encoding.UTF8.GetString(b);
}

static void Main(string[] args)
{

byte[] data = Encoding.UTF8.GetBytes("This is just a little message to test AES.");

byte[] key = { 7, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8,
1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8 };

byte[] enc = Encrypt(data, key);
byte[] dec = Decrypt(enc, key);

Console.WriteLine("Input : {0}", getString(data));
Console.WriteLine("Key : {0}", getString(key));
Console.WriteLine("KeySize : {0}", 256);
Console.WriteLine("Encrypted : {0}", getString(enc));
Console.WriteLine("Decrypted : {0}", getString(dec));

Console.ReadKey();

}

public static byte[] Encrypt(byte[] data, byte[] key)
{
using (AesCryptoServiceProvider csp = new AesCryptoServiceProvider())
{
csp.KeySize = 256;
csp.BlockSize = 128;
csp.Key = key;
csp.Padding = PaddingMode.PKCS7;
csp.Mode = CipherMode.ECB;
ICryptoTransform encrypter = csp.CreateEncryptor();
return encrypter.TransformFinalBlock(data, 0, data.Length);
}
}

private static byte[] Decrypt(byte[] data, byte[] key)
{
using (AesCryptoServiceProvider csp = new AesCryptoServiceProvider())
{
csp.KeySize = 256;
csp.BlockSize = 128;
csp.Key = key;
csp.Padding = PaddingMod

The code is simple to understand and does what it needs to do. Just some remarks:

• Whenever you use the ECB cipher mode, you must justify in written form why you use it. This is because this cipher mode can reveal patterns in your plain text.

• Converting the encrypted bytes to an UTF-8 string doesn't make sense. You should better print them in hex or base64.

-
Your code contains duplicates. You could extract that code into a method:

private AesCryptoServiceProvider CreateProvider(byte[] key) {
    return new AesCryptoServiceProvider {
        KeySize = 256,
        BlockSize = 128,
        Key = key,
        Padding = PaddingMode.PKCS7,
        Mode = CipherMode.ECB
    };
}

-
You made the Encrypt method public, but Decode is private. I don't see a reason for this asymmetry.

StackExchange Code Review Q#154017, answer score: 8