The values assigned in a PowerShell Execution Policy can trigger the "PowerShell is not a digitally signed" error. 

This error occurs sometimes when users run PowerShell scripts.

Here at Ibmi Media, as part of our Server Management Services, we regularly help our customers to fix Windows related issues.

Now, let us look into how to solve this error.

What causes PowerShell is not digitally signed error?

The  security error "PowerShell is not digitally signed" occurs when dealing with PowerShell Script which is not signed by a Trusted Publisher.

Additionally, when an AllSigned or RemoteSigned PoerShell Execution Policy is used, the security error can occur.

How to fix "PowerShell is not digitally signed" error?

To fix this error, different methods can be applied as will be shown below.

i. Inspect and Modify the Execution Policy.

To get the Execution Policy, simply run the "Get-ExecutionPolicy"  cmdlet. The policy for each scope is described by the parameter in the Get-ExecutionPolicy cmdlet as shown below;

PS C:\> Get-ExecutionPolicy -list

Additionally, you can set the execution policy to Unrestricted and modify the Execution Policy via the SetExecutionPolicy cmdlet by running the command below;

PS C:> Set-ExecutionPolicy unrestricted

Then when prompted to continue, Press "Y" to change the Policy.

ii. Bypassing the current PowerShell session

Another method of fixing this issue is by modifying the execution policy temporarily by running the Set-ExecutionPolicy cmdlet with Bypass setting as shown below;

Set-ExecutionPolicy -Scope Process -ExecutionPolicy  ByPass

This will help to set the execution policy to bypass the current PowerShell session. Since this is temporal, as soon as the PowerShell session is closed, the settings will be lost.

iii. Unblocking the downloaded file

You can sign all the scripts and its configuration files downloaded from an external source (Internet) or from a trusted publisher's email.

If the contents of the script are safe and trusted, then you can implement an unblock by running the Unblock-File cmdlet as shown below;

PS C:> Unblock-File -Path C:Downloadsscript1.ps1

Important values for ExecutionPolicy parameter

We will look briefly at the some acceptable values for -ExecutionPolicy parameter;

1. Restricted

This restricts the script from running and also prevent the configuration files from loading. It is regarded as the default execution policy.

2. AllSigned

This requires that a trusted publisher signs all script and configuration files including scripts written on the local computer.

3. RemoteSigned

All scripts and configuration files downloaded from the internet is signed by a trusted publisher.

4. Unrestricted

This allows all scripts and configuration files to load. However, you will be prompted for permission when trying to run an unsigned script downloaded from the internet.

5. Bypass

This allows Scripts and Configuration files to run without any interruptions or warnings.

6. Undefined

This takes off the currently assigned execution policy from the current scope. However, an execution policy configured in a Group Scope will not be altered.

LocalMachine is the default scope for Set-ExecutionPolicy command. By adding the "-Scope" parameter, you can specify the scope for policy. Some scopes you can work with includes the following;

Process: Only the current PowerShell process is affected by the execution policy.

CurrentUser: Only the current user is affected by the execution policy.

LocalMachine: Here, all users of the computer is affected by the execution policy.

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