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#)

Solution 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.

Solution 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.

Solution 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.

Solution 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

Solution 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.

View more solutions

Comments

[SQLMenace]

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

[LoganS]

Steven, these specific values are hardware specific.

[John MacIntyre]

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

[Steven Sudit]

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

[Steven Sudit]

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

[Steven Sudit]

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

[Scott Chamberlain]

@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.

[Scott Chamberlain]

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

[Steven Sudit]

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

[Steven Sudit]

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

[mattbasta]

@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.

[Steven Sudit]

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

[Steven Sudit]

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

[SQLMenace]

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

[irag10]

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.

[rizwan]

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

[Dig]

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.

[Steven Sudit]

@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.

[Steven Sudit]

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.

[Scott Chamberlain]

@Rory 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)

[pomarc]

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

[movAX13h]

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.".

[Skipper]

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\MachineGu‌​id ?

[qJake]

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

[bubi]

@qJake wich property?

[bubi]

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

[qJake]

@bubi 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.

[richard]

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 #.

[Scott Chamberlain]

@Skipper 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