(PowerShell) Get a Certificate's Key Size

Demonstrates how to get the RSA key size of a certificate (for example, 1024-bit, 2048-bit, etc.)

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# For this example, I have a certificate in raw base64 format (not PEM),
# that looks like this:  "MIIGkDCCBHigAwIBAgIUMDA ... s/iqLsLA=="
$sbCertBase64 = New-Object Chilkat.StringBuilder
$success = $sbCertBase64.LoadFile("qa_data/certs/base64Cert.txt","utf-8")

$cert = New-Object Chilkat.Cert
$success = $cert.LoadFromBase64($sbCertBase64.GetAsString())
if ($success -ne $true) {
    $($cert.LastErrorText)
    exit
}

# Get the public key.
$pubKey = $cert.ExportPublicKey()
if ($cert.LastMethodSuccess -ne $true) {
    $($cert.LastErrorText)
    exit
}

# In Chilkat version v9.5.0.67, the KeySize property was added.
$numBits = $pubKey.KeySize
$("Number of bits = " + $numBits)

# If using an older version of Chilkat, the key size can be obtained like this:
$xml = New-Object Chilkat.Xml
$xml.LoadXml($pubKey.GetXml())

$binDat = New-Object Chilkat.BinData
$binDat.AppendEncoded($xml.GetChildContent("Modulus"),"base64")

$numBits = 8 * $binDat.NumBytes
$("Number of bits = " + $numBits)