PGP File Decryption using C# and Command Line Utility

Posted on 2008-10-05
Last Modified: 2012-05-05
I am using C# and PGP Command Line tool for decrypting symmetric encrypted pgp files.
As far as I know, I can decrypt files using this command:
pgp --decrypt --symmetric-passphrase 123 --output D:\lic_mmm.txt D:\lic.txt.pgp

That decrypts D:\lic.txt.pgp to D:\lic_mmm.txt with passphrase as 123.

This works fine when using cmd, now I want to automate this process in C#.

My code looks like the code below.

But this is not working, the command window appears and then hides showing a message: "Invalid argument"

What is wrong with the code?
System.Diagnostics.Process p = new System.Diagnostics.Process();
                p.StartInfo.WorkingDirectory = @"D:\PGP Command Line";
                string args = @"--decrypt --symmetric-passphrase 123 --output D:\lic_mmm.txt D:\lic.txt.pgp";
                p.StartInfo.FileName = "pgp";
                p.StartInfo.Arguments = " " + args;

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Question by:Mortaza Doulaty
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LVL 12

Author Comment

by:Mortaza Doulaty
ID: 22643824
Using this code (using cmd with /c option) solved my problem, but what was wrong with my code?

                args = @"/c pgp --decrypt --symmetric-passphrase ""123"" --output ""D:\lic_mmm.txt"" ""D:\Lic.txt.pgp""";
                p.StartInfo.FileName = "cmd";

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LVL 33

Accepted Solution

Dave Howe earned 250 total points
ID: 22644368
well, just a comment, but personally I wouldn't do it that way - instead of using command line PGP (and paying for the privilege of starting a clunky command shell per crypto op) use the bouncy castle c# libraries instead
LVL 55

Assisted Solution

by:Jaime Olivares
Jaime Olivares earned 250 total points
ID: 22644446
I think you need to specify:
p.StartInfo.FileName = @"c:\fullpath\pgp";
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LVL 12

Author Comment

by:Mortaza Doulaty
ID: 22645387
>>p.StartInfo.FileName = @"c:\fullpath\pgp";

But I've specified .WorkingDirectory

Tried, no luck!

p.StartInfo.WorkingDirectory = @"D:\PGP Command Line";

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LVL 12

Author Comment

by:Mortaza Doulaty
ID: 22645391
>>well, just a comment, but personally I wouldn't do it that way - instead of using command

I'll try this too.

I've tried GnuPG, it is working fine...
LVL 33

Expert Comment

by:Dave Howe
ID: 22645449
gnupg is an option, and is at least free - but you are still having to start a command shell to run the command each time. a native library is much better :)
LVL 12

Author Comment

by:Mortaza Doulaty
ID: 22645710
>>but you are still having to start a command shell to run
Using a process (as in my previous code) solves the problem.

Tomorrow, I will check the native class you provided.
LVL 12

Author Comment

by:Mortaza Doulaty
ID: 22648990
Dear jaime_olivares,
  This worked for me:
    p.StartInfo.FileName = @"c:\fullpath\pgp.exe";

Dear DaveHowe,
  I tested Bouncy Castle tool and it worked fine, I'm gonna use this.

Thanks for your helps.

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