Question

GPG decryption via command-line?

Asked by: mdoolittle

I have a PGP-encrypted file which I download and decrypt on my machine (currently via the GPG Windows GUI). Call the file 'MyFile.gpg'.

I want to automate the decryption of this file. However I can't seem to locate a reference detailing the command-line syntax necessary.

I did find this: gpg  --batch --passphrase-fd 0 --decrypt test-target.txt.gpg --output test-target.txt < pass.txt
http://www.experts-exchange.com/Security/Encryption/Q_22949543.html

But I'm not sure what the parameters mean or how to structure the statement I'll need. First, is there a reference online simply outlining the command-line syntax for GPG under Windows?

Second, what is the exact syntax I'd use to decrypt 'C:\MyFile.gpg' to 'C:\MyDecryptedFile.xxx'? How do I point toward my private key? I will ultimately wrap this in a VBScript and will pass my passphrase via an InputBox.

Thanks!

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Asked On
2009-11-06 at 10:52:11ID24878900
Tags

GPG

,

decryption

,

DOS

,

command-line

Topics

VB Script

,

Encryption for Network Security

,

MS DOS

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Answers

 

by: TheNauticanPosted on 2009-11-06 at 14:50:12ID: 25763770

there seem to be several flavors floating around out there.
Here is one online manual http://www.gnupg.org/documentation/manuals/gnupg/

 

by: mdoolittlePosted on 2009-11-09 at 13:03:59ID: 25780043

Got it!

This is the command-line syntax:
"C:\Program Files\GnuPG\gpg.exe" --passphrase "My passphrase" -o "C:\MyFile.txt" -d "C:\MyFile.pgp"

The order of the parameters matters...you can't put '-d' before '-o', for example (not sure about switching '--passphrase' with '-o').

Here is a VBScript example:

Option Explicit 
Dim bWaitOnReturn: bWaitOnReturn = True
Dim iWindowStyle: iWindowStyle = 7 'Minimized; active window stays active
Dim sPassphrase: sPassphrase = InputBox("Enter passphrase","Passphrase")
Dim sFileName_Output: sFileName_Output = "C:\MyDecryptedFile.txt"
Dim sFileName_Input: sFileName_Input = "C:\MyEncryptedFile.pgp"
Dim sCommand_Text: sCommand_Text = Chr(34) & "C:\Program Files\GnuPG\gpg.exe" & Chr(34) & "--passphrase " & Chr(34) & sPassphrase & Chr(34) & " -o " & Chr(34) & sFileName_Output & Chr(34) & " -d " & Chr(34) & sFileName_Input & Chr(34)
Dim oWiSH_Shell: Set oWiSH_Shell = CreateObject("WScript.Shell")
oWiSH_Shell.Run sCommand_Text, iWindowStyle, bWaitOnReturn
Set oWiSH_Shell = Nothing
WScript.Quit

                                              
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