(PowerShell) About RSA Public/Private Keys

This example provides some additional information for understanding public/private key pairs. In demonstrates how a private key is a superset of the public key. A public key contains the modulus and exponent. The matching private key also contains the modulus and exponent, but also contains the additional private key parts.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat .NET Downloads Chilkat .NET Assemblies

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

$success = $false

$cert = New-Object Chilkat.Cert

# Load a digital certificate.
$success = $cert.LoadFromFile("digitalCert.cer")
if ($success -eq $false) {
    $($cert.LastErrorText)
    exit
}

# A .cer file does not contain the private key.  It should contain
# the public key...
$pubKey = New-Object Chilkat.PublicKey
$cert.GetPublicKey($pubKey)

# Let's have a look at it (in XML format).
$("Public Key from Certificate:")
$($pubKey.GetXml())

# An RSA public key consists of a modulus and exponent.

# An RSA private key includes both the modulus and exponent,
# as well as other "big" numbers: P, Q, D, etc.

# Let's load an RSA private key from a DER-encoded file:
$privKey = New-Object Chilkat.PrivateKey

$success = $privKey.LoadAnyFormatFile("PrivateKey.key","")
if ($success -ne $true) {
    $($privKey.LastErrorText)
    exit
}

# If this private key is the matching half to the public key from
# the certificate, then the modulus and exponent should
# be identical.  (Thus, a "private key" really contains both the public part as well as the private parts...).
$("Private Key from DER:")
$($privKey.GetXml())