Get-CodeSigningKeyContainer.ps1

param
(
    [Parameter(Mandatory=$false)][switch]$Quiet=$false
)

function Get-CodeSigningKey() {
    $childItem = Get-ChildItem cert:\CurrentUser\My -codesign | Where-Object { 
        $($_.EnhancedKeyUsageList | Select-Object -ExpandProperty FriendlyName | Where-Object { 
            $_ -eq "Code Signing"
        }) -ne $null        
    }
    if ($childItem -ne $null) {
        return "cert:CurrentUser\My\$($childItem.Thumbprint)"
    }
    Write-Error "Could not find a code signing key in this user's personal certificate store"
    return $null
}

function Get-KeyContainer {
    param(
        [Parameter(Mandatory=$true)][string]$path
    )
    process {
        $cert=$(Get-Item $path)
        return $($cert.PrivateKey.CspKeyContainerInfo.KeyContainerName)
    }
}

$Script:CertPath=$(Get-CodeSigningKey)

if ($Script:CertPath -ne $null) {
    $Script:Key=Get-Item $Script:CertPath
    if ($Quiet) {
        Write-Host "$(Get-KeyContainer $CertPath)"
    }
    else {
        Write-Host "Code Signing Key Located"
        Write-Host "Subject: $($Key.Subject)"
        Write-Host "Thumbprint: $($Key.Thumbprint)"
        Write-Host "Container Name: '$(Get-KeyContainer $CertPath)'"
    }    
}
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# SIG # End signature block

Does not work if there are several code-signing certificates in Personal store. Had to delete all but the leaf one which is not ideal.

Btw, can use certutil -user -store my "{{thumbnail}}" to dump key container instead.