Create a Self-Signed Certificate Using PowerShell
In today’s Ask the Admin, I’ll show you how to quickly create a self-signed certificate.
Self-signed certificates are not recommended for use in production environments, but come in handy for test scenarios where a certificate is a requirement but you don’t have the time or resources to either buy a certificate or deploy your own Public Key Infrastructure (PKI).
But generating self-signed certificates in Windows has traditionally been a bit of a pain, at least if you didn’t have Visual Studio or IIS on hand, as both these products include the ability to generate self-signed certificates. The makecert command line tool was otherwise the “go to” tool, but was only available as part of the Windows SDK, which is a hefty product to download and install just for the sake of using makecert.
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Starting in PowerShell version 4.0, Microsoft introduced the New-SelfSignedCertificate cmdlet, making it much easier to create self-signed certificates. To get started, you’ll need a Windows device running PowerShell 4.0 or higher.
- Open a PowerShell prompt. In Windows 10, type powershell in the search dialog on the taskbar, right-click Windows PowerShell in the list of app results, select Run as administrator from the menu and then enter an administrator username and password. The New-SelfSignedCertificate can only install certificates to the My certificate store, and that requires local administrator rights on the device.
- If you’re running a different version of Windows, check the PowerShell version by running the code shown below.
If you need to update PowerShell to version 5, you can download the Windows Management Framework for Windows 7 and Windows 8.1 here.
- Now run the New-SelfSignedCertificate cmdlet as shown below to add a certificate to the local store on your PC, replacing testcert.petri.com with the fully qualified domain name (FQDN) that you’d like to use.
$cert = New-SelfSignedCertificate -certstorelocation cert:\localmachine\my -dnsname testcert.petri.com
The next step is to export a self-signed certificate. But first we’ll need to create a password as shown below:
$pwd = ConvertTo-SecureString -String ‘passw0rd!’ -Force -AsPlainText
Now we can export a self-signed certificate using the Export-PfxCertificate cmdlet. We’ll use the password ($pwd) created above, and create an additional string ($path), which specifies the path to the certificate created with New-SelfSignedCertificate cmdlet.
$path = 'cert:\localMachine\my\' + $cert.thumbprint Export-PfxCertificate -cert $path -FilePath c:\temp\cert.pfx -Password $pwd
Note that the c:\temp directory, or whatever directory you specify in the -FilePath parameter, must already exist. You can now import the cert.pfx file to install the certificate.