(PowerShell) Convert PuTTY Private Key (ppk) to OpenSSH (pem)

Convert a PuTTY format private key file (.ppk) to OpenSSH (.pem).

Download: Chilkat .NET Assemblies

[Reflection.Assembly]::LoadFile("C:\myAssemblies\ChilkatDotNet2.dll")

$key = New-Object Chilkat.SshKey

#  Load an unencrypted or encrypted PuTTY private key.

#  If  your PuTTY private key is encrypted, set the Password
#  property before calling FromPuttyPrivateKey.
#  If your PuTTY private key is not encrypted, it makes no diffference
#  if Password is set or not set.
$key.Password = "secret"

#  First load the .ppk file into a string:

$keyStr = $key.LoadText("putty_private_key.ppk")

#  Import into the SSH key object:
$success = $key.FromPuttyPrivateKey($keyStr)
if ($success -ne $true) {
    $($key.LastErrorText)
    exit
}

#  Convert to an encrypted or unencrypted OpenSSH key.

#  First demonstrate converting to an unencrypted OpenSSH key

$bEncrypt = $false
$unencryptedKeyStr = $key.ToOpenSshPrivateKey($bEncrypt)
$success = $key.SaveText($unencryptedKeyStr,"unencrypted_openssh.pem")
if ($success -ne $true) {
    $($key.LastErrorText)
    exit
}

#  Save to an encrypted OpenSSH PEM file:

$bEncrypt = $true
$key.Password = "myPassword"
$encryptedKeyStr = $key.ToOpenSshPrivateKey($bEncrypt)
$success = $key.SaveText($encryptedKeyStr,"encrypted_openssh.pem")
if ($success -ne $true) {
    $($key.LastErrorText)
    exit
}

$("Done!")