public void Challenge7()
{
var encrypted = Convert.FromBase64String(File.ReadAllText(TestContext.CurrentContext.TestDirectory + "\\resources\\7.txt"));
var output = Encoding.UTF8.GetString(AES128.DecryptECB(encrypted, Encoding.UTF8.GetBytes("YELLOW SUBMARINE")));
Assert.IsTrue(output.StartsWith("I'm back and I'm ringin' the bell"));
}