Generating Unique Key (Finger Print) for a Computer for Licensing Purposes

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Introduction

For licensing purposes, according to me, the best and secure way is to generate a unique key for the client's machine and provide a corresponding license key for that key. For this purpose, you can take help of the unique id of the client's computer motherboard, BIOS and processor. When you get these IDs, you can generate any key of your preferable format.
Year ago, I found a very handy and useful code in C# by searching the Internet to get these IDs. And it's serving me perfectly so far. Thanks to the original author of the code.
I added some additional code to generate a 128 bit key of a machine. The output is a nice looking key in hexadecimal format (eg. 4876-8DB5-EE85-69D3-FE52-8CF7-395D-2EA9).

Suggestions

I have a few suggestions in this regard:

• Generate a key from only the Motherboard, Processor and BIOS since the user normally doesn't change these parts.
• Don't use MAC ID, Graphics Card ID AND Disk ID since it's very common to change these devices.
• It takes significant time to get IDs of devices. So make the finger print generating function static and save it in a static variable so that it generates the key only once in the whole application.

The Code

Here is the class. The code in the region "Original Device ID Getting Code" is from the original author.

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using System;
using System.Management;
using System.Security.Cryptography;
using System.Security;
using System.Collections;
using System.Text;
namespace Security
{
    /// <summary>
    /// Generates a 16 byte Unique Identification code of a computer
    /// Example: 4876-8DB5-EE85-69D3-FE52-8CF7-395D-2EA9
    /// </summary>
    public class FingerPrint  
    {
        private static string fingerPrint = string.Empty;
        public static string Value()
        {
            if (string.IsNullOrEmpty(fingerPrint))
            {
                fingerPrint = GetHash("CPU >> " + cpuId() + "\nBIOS >> " + 
   biosId() + "\nBASE >> " + baseId()
                            //+"\nDISK >> "+ diskId() + "\nVIDEO >> " + 
   videoId() +"\nMAC >> "+ macId()
                                     );
            }
            return fingerPrint;
        }
        private static string GetHash(string s)
        {
            MD5 sec = new MD5CryptoServiceProvider();
            ASCIIEncoding enc = new ASCIIEncoding();
            byte[] bt = enc.GetBytes(s);
            return GetHexString(sec.ComputeHash(bt));
        }
        private static string GetHexString(byte[] bt)
        {
            string s = string.Empty;
            for (int i = 0; i < bt.Length; i++)
            {
                byte b = bt[i];
                int n, n1, n2;
                n = (int)b;
                n1 = n & 15;
                n2 = (n >> 4) & 15;
                if (n2 > 9)
                    s += ((char)(n2 - 10 + (int)'A')).ToString();
                else
                    s += n2.ToString();
                if (n1 > 9)
                    s += ((char)(n1 - 10 + (int)'A')).ToString();
                else
                    s += n1.ToString();
                if ((i + 1) != bt.Length && (i + 1) % 2 == 0) s += "-";
            }
            return s;
        }
        #region Original Device ID Getting Code
        //Return a hardware identifier
        private static string identifier
  (string wmiClass, string wmiProperty, string wmiMustBeTrue)
        {
            string result = "";
            System.Management.ManagementClass mc = 
  new System.Management.ManagementClass(wmiClass);
            System.Management.ManagementObjectCollection moc = mc.GetInstances();
            foreach (System.Management.ManagementObject mo in moc)
            {
                if (mo[wmiMustBeTrue].ToString() == "True")
                {
                    //Only get the first one
                    if (result == "")
                    {
                        try
                        {
                            result = mo[wmiProperty].ToString();
                            break;
                        }
                        catch
                        {
                        }
                    }
                }
            }
            return result;
        }
        //Return a hardware identifier
        private static string identifier(string wmiClass, string wmiProperty)
        {
            string result = "";
            System.Management.ManagementClass mc = 
  new System.Management.ManagementClass(wmiClass);
            System.Management.ManagementObjectCollection moc = mc.GetInstances();
            foreach (System.Management.ManagementObject mo in moc)
            {
                //Only get the first one
                if (result == "")
                {
                    try
                    {
                        result = mo[wmiProperty].ToString();
                        break;
                    }
                    catch
                    {
                    }
                }
            }
            return result;
        }
        private static string cpuId()
        {
            //Uses first CPU identifier available in order of preference
            //Don't get all identifiers, as it is very time consuming
            string retVal = identifier("Win32_Processor", "UniqueId");
            if (retVal == "") //If no UniqueID, use ProcessorID
            {
                retVal = identifier("Win32_Processor", "ProcessorId");
                if (retVal == "") //If no ProcessorId, use Name
                {
                    retVal = identifier("Win32_Processor", "Name");
                    if (retVal == "") //If no Name, use Manufacturer
                    {
                        retVal = identifier("Win32_Processor", "Manufacturer");
                    }
                    //Add clock speed for extra security
                    retVal += identifier("Win32_Processor", "MaxClockSpeed");
                }
            }
            return retVal;
        }
        //BIOS Identifier
        private static string biosId()
        {
            return identifier("Win32_BIOS", "Manufacturer")
            + identifier("Win32_BIOS", "SMBIOSBIOSVersion")
            + identifier("Win32_BIOS", "IdentificationCode")
            + identifier("Win32_BIOS", "SerialNumber")
            + identifier("Win32_BIOS", "ReleaseDate")
            + identifier("Win32_BIOS", "Version");
        }
        //Main physical hard drive ID
        private static string diskId()
        {
            return identifier("Win32_DiskDrive", "Model")
            + identifier("Win32_DiskDrive", "Manufacturer")
            + identifier("Win32_DiskDrive", "Signature")
            + identifier("Win32_DiskDrive", "TotalHeads");
        }
        //Motherboard ID
        private static string baseId()
        {
            return identifier("Win32_BaseBoard", "Model")
            + identifier("Win32_BaseBoard", "Manufacturer")
            + identifier("Win32_BaseBoard", "Name")
            + identifier("Win32_BaseBoard", "SerialNumber");
        }
        //Primary video controller ID
        private static string videoId()
        {
            return identifier("Win32_VideoController", "DriverVersion")
            + identifier("Win32_VideoController", "Name");
        }
        //First enabled network card ID
        private static string macId()
        {
            return identifier("Win32_NetworkAdapterConfiguration", 
    "MACAddress", "IPEnabled");
        }
        #endregion
    }
}