What is a good unique PC identifier?

Question

I've been looking at the code in this tutorial, and I found that it uses My.Computer.Name to save settings that shouldn't roam between computers. It's entirely possible, however, for a user to have two identically named PCs. If they wanted to have the same username on each PC, for example, they may very well end up with two PCs named Username-PC.

What are some good methods of identifying different PCs? Do PCs have GUIDs associated with them, or should I look into pulling the serial number off of some hardware? I don't care if the identification persists through reinstallation of Windows.

(The tutorial I linked is in VB.Net, but I'm implementing it in C#)

Artur

#672376 – Dunnite

#100380 – Dunnite

Answer 1

Some good identifiers:

• MAC Address: It's fairly easy to get at, and it's usually unique. However, it can be spoofed/changed rather easily, so it depends on how unique it needs to be.
• CPU Serial Number: It's not available on lots of older systems, but it's there. Check out this MSDN page. It won't change, but it's bound to a computer.
• HDD Serial Number: It's likely to not change, but can be a nuisance if the HD fails. Check out this MSDN page.

Solicitous

+1 Yeah, be careful with the MAC. I had a ton of problems before with the MAC changing & being duplicated. PITA. – Williemaewillies

Careful: I've seen cases where the CPU (of a laptop) got toasted and had to be replaced. New CPU, new CPUID. – Nassi

@Steven: Good point. Generally, though, I'd consider it one of the "most reliable" IDs on a system. CPU failure is relatively uncommon (compared to HD failure). It should also be noted that this number might get gummed up when you start dealing with virtualization. – Solicitous

Yes, virtualization sounds like a more likely reason for all sorts of failures, as compared to hardware changes. – Nassi

According to MSDN: This property is not supported before Windows Server 2016 Technical Preview and Windows 10. Not really viable yet. :( – Boxing

@Boxing wich property? – Hydranth

Another reason about avoid MAC: I think that MAC address of the first enabled card is not a good idea for laptops (I still have not solved my issues and I'm searching for a different solution). They change the card if you attach a network cable then use WiFi – Hydranth

@Hydranth The SerialNumber property that gets the CPU serial. Look on your MSDN link and Ctrl+F "SerialNumber" and read the last note on operating systems for that property. – Boxing

Answer 2

If you are on windows HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\ CurrentVersion\ProductId is unique per machine/per windows install. where as in some of the other answers like the MAC address, Proc SN, and HD SN will stay the same between windows reinstalls/dual boot situations.

Standoffish

Is this the number used by Windows to detect when it's been installed onto a different machine? – Nassi

@Steven Sudit, Yes, I believe this number is generated by a hash of several pieces of HW information, the windows serial key and a timestamp. When you activate windows they send the serial key and this code and store the code on their servers. – Standoffish

Here is a wiki page talking about how they are generated wiki.lunarsoft.net/wiki/Product_IDs – Standoffish

Well, the positive here is that anything capable of changing this product ID will also be a major pain to Windows itself. :-) – Nassi

Isn't that just the license key used at windows install? In which case it'll be the same on different machines that were installed from the same image. – Cambric

@Cambric I believe that performing a sysprep will cause that ID to change upon the first time you start the system (and if you are using system images you really should be using sysprep) – Standoffish

This key is not present on my W8.1 64bit – Dunton

I know it's been a while, but today I found an other answer here and thus I wonder what is the difference between ids in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\ CurrentVersion\ProductId and in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\MachineGuid ? – Desmarais

@Desmarais ProductId is a unique id used with windows installs. MachineGuid is used when you use the windows encryption system when you a "Protect Data" on the "local machine" scope – Standoffish

Today, after an update for Windows 11, version 22H2, my ProductId just changed. So this does not seem to be a very stable identifier. – Furunculosis

Answer 3

The real answer to that question: There is no such thing.

There are several "close enough" solutions, but each one of those has it's own limitation.

All the hardware IDs - Hardware changes. And, in many cases you can change those identifiers (For example, MAC spoofing).

The SID, as I've already commented, Is not that good as well, because the SID won't change if the computer was installed from an image. The SID is generated by windows installation, if windows wasn't installed, but copied from an image, the SID won't change (although it is common to regenerate it because of a myth about "security risk" - you can't count on that).

Computer name - Well, as mentioned, They suppose to be unique, but it's not enforced in any way.

Another solution you can implement is to generate you own unique identifier and store it locally (assuming you can do such thing). Again, this solution won't work if your computer was imaged with your application.

The best solution for you really depends on what you are trying to accomplish. I had the same problem with a quite large network, and the best solution in my case was the computer's name. If you are absolutely sure that your process won't be imaged, I would generate a unique identifier using Guid because it will probably be the safest.

Surra

Answer 4

Here is a way to uniquely identify a computer. Using System.Management to get Win32_BIOS, you can get unique values from your machine's BIOS.

See: Win32_BIOS class, http://msdn.microsoft.com/en-us/library/aa394077.aspx

using System.Management;

string UniqueMachineId()
{
    StringBuilder builder = new StringBuilder();

    String query = "SELECT * FROM Win32_BIOS";
    ManagementObjectSearcher searcher = new ManagementObjectSearcher(query);
    //  This should only find one
    foreach (ManagementObject item in searcher.Get())
    {
        Object obj = item["Manufacturer"];
        builder.Append(Convert.ToString(obj));
        builder.Append(':');
        obj = item["SerialNumber"];
        builder.Append(Convert.ToString(obj));
    }

return builder.ToString();
}

With similar logic, you can also step through "Win32_DiskDrive"; http://msdn.microsoft.com/en-us/library/aa394132.aspx; and get "SerialNumber" for each physical drive. In this case, the

    foreach (ManagementObject item in searcher.Get())

should find multiple items

Larrup

It's quite unsafe to use the Bios serial number since you might get a lot of these (identical!) strings: "To be filled by O.E.M.". – Mortar

Answer 5

Take three identifiers that are semi-unique and semi-constant. Use the rule that 2 out of 3 is sufficient for a positive identification. Update the registered data for the 1 out of 3 that is occasionally wrong.

Nonconformist

This is the only right answer. They need to cover the range of potentially replaceable parts. I would use BIOS serial number, HDD Id, Windows Serial #. – Tweeter

Answer 6

Use the network card's MAC address. It's supposed to be unique. It can be changed, though. It depends on how malicious you expect your users to be and how critical your application is.

Some sample code to do it:

public string GetMACAddress() {
    ManagementClass mc = new ManagementClass("Win32_NetworkAdapterConfiguration");
    ManagementObjectCollection moc = mc.GetInstances();

    string MACAddress = String.Empty;

    foreach (ManagementObject mo in moc) {
        if (MACAddress == String.Empty) { // only return MAC Address from first card
            if ((bool)mo["IPEnabled"] == true) MACAddress = mo["MacAddress"].ToString();
        }
        mo.Dispose();
    }

    return MACAddress;
}

Rohrer

Answer 7

One thing you can use is the MAC of any Network interface. You can also combine several sources of information. Like HDD Serial number, mac, processor type to calculate a hash from it.

Wallache

The more sources you use, the more reliable it is. However, the more sources you use, the more vulnerable you are to false positives. – Nassi

Answer 8

We use a combination of the ProcessorID from Win32_processor and the UUID from Win32_ComputerSystemProduct:

ManagementObjectCollection mbsList = null;
ManagementObjectSearcher mos = new ManagementObjectSearcher("Select ProcessorID From Win32_processor");
mbsList = mos.Get();
string processorId = string.Empty;
foreach (ManagementBaseObject mo in mbsList)
{
    processorId = mo["ProcessorID"] as string;
}

mos = new ManagementObjectSearcher("SELECT UUID FROM Win32_ComputerSystemProduct");
mbsList = mos.Get();
string systemId = string.Empty;
foreach (ManagementBaseObject mo in mbsList)
{
    systemId = mo["UUID"] as string;
}

var compIdStr = $"{processorId}{systemId}";

Previously, we used a combination: processor ID ("Select ProcessorID From Win32_processor") and the motherboard serial number ("SELECT SerialNumber FROM Win32_BaseBoard"), but then we found out that the serial number of the motherboard may not be filled in, or it may be filled in with uniform values:

• To be filled by O.E.M.
• None
• Default string

Therefore, it is worth considering this situation.

Also keep in mind that the ProcessorID number may be the same on different computers.

Outstretched

So the ProcessorID can be the same on different computers, and the SerialNumber can be empty or be a default value for both systems? – Furunculosis

Answer 9

I don't think it's possible to have two PC's with the same name on the same domain. Have you tried capturing the domain name?

Crissy

I have 2 PCs on the same domain with the same name :-) I dual boot between xp and win 7...although haven't booted into xp fr over 2 weeks now – Basketwork

@SQLMenace: Unless that have the same SID, the network still sees them as different boxes. – Nassi

It is the same box..I had to do some fancy stuff to make it to the domain from both boxes – Basketwork

Answer 10

Take a look here: Getting Service Tag from Dell Machine using .net?

You could snatch some unique data from the registry.

Pyrosis

Steven, these specific values are hardware specific. – Pyrosis

Hardware changes. Disc drives, CPU's, all of it. When it breaks, it's replaced. – Nassi

Answer 11

Each computer has a SID that's unique under normal circumstances.

Nassi

why is this the accepted answer? What is this SID and how to obtain it? – Aerostation

And it's even not correct. Please remove the mark from this answer. The SID (security identifier) is an identifier generated when you install windows. It is very unlikely that two computers will have the same SID. The SID was originally designed in order to identify users uniquely across a network. Why isn't it good enough? Because if the computer was not installed from scratch, but was installed from an image, then it will have the same SID of the original computer. This method for installing computers is very common in large networks, therefor SID is a bad choice in practice. – Surra

@DiGMi, you're right about cloning resulting in the same SID. That's why I said "under normal circumstances". As you mentioned in your response, some companies that install clone images do regenerate the SID. – Nassi

The problem is that there is no right answer universally, just answers that work better or worse depending on circumstances. It sounds like the OP is more concerned about avoiding a false match than having a false mismatch, in which case the CPU or HD ID's would work best. – Nassi

Answer 12

In a managed network environment, the best, most reliable identifier might be the one you create, but there are some downsides.

Some (many?) manufacturers provide a utility that allows you to set an asset tag that is stored in the firmware. This might be a bootable utility, or it might run within Windows, or it might even be built into the firmware setup. This "tag" is an arbitrary text string that you can set to whatever you want, and then read it back using WMI and the Win32_SystemEnclosure class...

string[] selectedProperties = new string[] { "SMBIOSAssetTag" };
ObjectQuery enclosureQuery = new SelectQuery("Win32_SystemEnclosure", null, selectedProperties);

using (ManagementObjectSearcher enclosureSearcher = new ManagementObjectSearcher(enclosureQuery))
using (ManagementObjectCollection enclosureCollection = enclosureSearcher.Get())
{
    foreach (ManagementObject enclosure in enclosureCollection)
    {
        string assetTag = (string) enclosure.GetPropertyValue("SMBIOSAssetTag");
    }
}

Pros:

• You can use whatever scheme you want (e.g. incorporating date, department, incrementing integers, GUIDs, etc.).
• You can use one scheme for all machines regardless of their manufacturer, instead of having to handle manufacturer-specific schemes.
• By allocating and tracking the identifiers yourself, you can guarantee that they are unique. Not relying on an identifier set by the manufacturer means there is no risk of duplicates within a manufacturer or between manufacturers.
• The identifier is stored in the firmware — not on the hard drive — so it will survive reformatting, upgrades, etc. but also not be duplicated by backups/imaging/cloning.

Cons:

• You need to actually set the asset tag; they'll all be blank until you do so.
• Setting a machine's asset tag may require physical access and a reboot.
• Asset tags are not write-once and could, therefore, be changed or erased.
  • Password-protected firmware should require that password before changing the tag, but that's not guaranteed.
• By allocating and tracking the identifiers yourself, there's not only the overhead of...allocating and tracking the identifiers, but also the possibility that you'll introduce duplicates if you're not careful.
• Using asset tags for this purpose requires that all machines support setting an asset tag and properly report it to WMI.

Venlo

Answer 13

There is a sample code with complete notes in this link for getting CPU and HD Drive ID: http://www.vcskicks.com/hardware_id.php

add this dll to refrences

 System.Management.dll

for CPU ID:

string cpuInfo = string.Empty;
ManagementClass mc = new ManagementClass("win32_processor");
ManagementObjectCollection moc = mc.GetInstances();

foreach (ManagementObject mo in moc)
{
     if (cpuInfo == "")
     {
          //Get only the first CPU's ID
          cpuInfo = mo.Properties["processorID"].Value.ToString();
          break;
     }
}
return cpuInfo;

and for Hard Drive ID (Volume Serial):

ManagementObject dsk = new ManagementObject(@"win32_logicaldisk.deviceid=""" + drive + @":""");
dsk.Get();
string volumeSerial = dsk["VolumeSerialNumber"].ToString();

Autarch