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Convert a PuTTY Private Key (.ppk) to OpenSSH (.pem)

Demonstrates converting a PuTTY format private key to OpenSSH format. The .ppk is imported with FromPuttyPrivateKey and re-exported with ToOpenSshPrivateKey, both unencrypted and encrypted.

Note: The file paths are relative to the application's current working directory. Supply the paths to your own files.

Background: PuTTY and OpenSSH store the same underlying key material in different container formats, so converting between them is a re-encoding rather than a new key — the corresponding public key, and therefore the server-side authorized_keys entry, is unchanged. This matters when moving between Windows tooling built around PuTTY and Unix tooling that expects PEM. Note that the Password property serves double duty: it decrypts the key on import and encrypts it on export, so set it appropriately for each step.

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Local $bSuccess = False

;  Demonstrates converting a PuTTY format private key (.ppk) to OpenSSH (.pem) format.

$oKey = ObjCreate("Chilkat.SshKey")

;  Set the password before importing an encrypted PuTTY key.  If the key is not encrypted it
;  makes no difference whether Password is set.  This should come from a secure source rather
;  than being hard-coded.
$oKey.Password = "myKeyPassword"

;  LoadText is a convenience method that reads any text file into a string.  It does not itself
;  load the key.
Local $sKeyStr = $oKey.LoadText("qa_data/putty_private_key.ppk")
If ($oKey.LastMethodSuccess = False) Then
    ConsoleWrite($oKey.LastErrorText & @CRLF)
    Exit
EndIf

$bSuccess = $oKey.FromPuttyPrivateKey($sKeyStr)
If ($bSuccess = False) Then
    ConsoleWrite($oKey.LastErrorText & @CRLF)
    Exit
EndIf

;  Export to an unencrypted OpenSSH key.
Local $bEncrypt = False
Local $sUnencryptedKeyStr = $oKey.ToOpenSshPrivateKey($bEncrypt)
If ($oKey.LastMethodSuccess = False) Then
    ConsoleWrite($oKey.LastErrorText & @CRLF)
    Exit
EndIf

$bSuccess = $oKey.SaveText($sUnencryptedKeyStr,"qa_output/unencrypted_openssh.pem")
If ($bSuccess = False) Then
    ConsoleWrite($oKey.LastErrorText & @CRLF)
    Exit
EndIf

;  Export to an encrypted OpenSSH key.  The Password property supplies the passphrase used to
;  encrypt the output.
$bEncrypt = True
$oKey.Password = "myExportPassword"
Local $sEncryptedKeyStr = $oKey.ToOpenSshPrivateKey($bEncrypt)
If ($oKey.LastMethodSuccess = False) Then
    ConsoleWrite($oKey.LastErrorText & @CRLF)
    Exit
EndIf

$bSuccess = $oKey.SaveText($sEncryptedKeyStr,"qa_output/encrypted_openssh.pem")
If ($bSuccess = False) Then
    ConsoleWrite($oKey.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Done!" & @CRLF)