Encrypt.cs

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

public class Encrypt : ScriptableObject
{
	public static byte[] EncryptBytes(byte[] message, byte[] rgbKey, byte[] rgbIV)
	{
		if ((message == null) || (message.Length == 0))
			return null;
		using (var stream = new MemoryStream())
			using (var encrypter = new RijndaelManaged().CreateEncryptor(rgbKey, rgbIV))
				using (var encrypt = new CryptoStream(stream, encrypter, CryptoStreamMode.Write))
		{
			encrypt.Write(message, 0, message.Length);
			encrypt.FlushFinalBlock();
			return stream.ToArray();
		}
	}
	public static byte[] DecryptBytes(byte[] encrypted, byte[] rgbKey, byte[] rgbIV)
	{
		if ((encrypted == null) || (encrypted.Length == 0))
			return null;
		using (var stream = new MemoryStream())
			using (var decrypter = new RijndaelManaged().CreateDecryptor(rgbKey, rgbIV))
				using (var encrypt = new CryptoStream(stream, decrypter, CryptoStreamMode.Write))
		{
			encrypt.Write(encrypted, 0, encrypted.Length);
			encrypt.FlushFinalBlock();
			return stream.ToArray();
		}
	}
}

encrypt.py

# -*- coding: utf-8 -*-

import base64
import Crypto.Cipher.AES as AES

iv = base64.b64decode("zlW3vcM3s06ZC1uVJ/ZieQ==")
dec = AES.new("abcdefghijklmnopqrstuvwxyz012345", AES.MODE_CBC, iv)
print dec.decrypt(base64.b64decode("EUmkubX1UQ/z/R93L/JRRw=="))

EncryptTest.cs

using System;
using System.Text;
using System.Security.Cryptography;
using NUnit.Framework;

namespace AssemblyCSharp
{
	[TestFixture()]
	public class EncryptTest
	{
		[Test()]
		public void TestCase ()
		{
			string expected = "sample";
			string seed = "abcdefghijklmnopqrstuvwxyz012345";
			byte[] message = Encoding.UTF8.GetBytes(expected);
			using (RijndaelManaged myRijndael = new RijndaelManaged())
			{
				myRijndael.Key = Encoding.UTF8.GetBytes(seed);
				myRijndael.GenerateIV();
				Console.WriteLine(Convert.ToBase64String(myRijndael.IV));
				Console.WriteLine(myRijndael.Mode);
				byte[] encrypted = Setting.EncryptBytes(message, myRijndael.Key, myRijndael.IV);
				byte[] decrytped = Setting.DecryptBytes(encrypted, myRijndael.Key, myRijndael.IV);
				var actual = Encoding.UTF8.GetString(decrytped);
				Console.WriteLine(Convert.ToBase64String(encrypted));
				Assert.AreEqual(expected, actual);
			}
		}
	}
}