CTB=55 cannot decrypt message from PGP 9 because of comment line

[David Shaw]

On Sep 1, 2008, at 7:11 AM, emnej at web.de wrote:

> This is my first message on the list and it immediately is a request  
> for help ;-)
>
> I used to use PGP with Pegasus Mail but switched my email system to  
> Thunderbird + GnuPG + Enigmail. I often receive encrypted emails,  
> from a variety of people. I have noticed that I regularly have the  
> following problem:
>
> When trying to decrypt a message that comes from someone with PGP 9,  
> I get the following error:
>
> gpg.exe --charset utf8  --batch --no-tty --status-fd 2 -d -- 
> passphrase-fd 0 --no-use-agent ,gpg: invalid radix64 character 3A  
> skipped,gpg: invalid radix64 character 2E skipped,gpg: invalid  
> radix64 character 2E skipped,gpg: invalid radix64 character 28  
> skipped,gpg: invalid radix64 character 29 skipped,gpg: invalid  
> radix64 character 3A skipped,gpg: invalid radix64 character 2D  
> skipped,gpg: CRC error; 188EB4 - 9C15D0,gpg: [don't know]: invalid  
> packet (ctb=55)
>
> PGP has no problems decrypting these messages. When I remove the  
> comment lines inserted by PGP (e.g. Version: PGP Desktop 9.8.3  
> (Build 4028), GnuPG can also decrypt the messages without any  
> problems.
>
> My question is if there is a work around for this, or if there is an  
> option that can be used so that the comment line does not interfere  
> with the decryption.

This come up now and then.  The problem, as you noted, is the comment  
line.  Basically, the PGP comment line is long enough that many  
mailers word-wrap it.  Thus, the message that gets passed to GPG is  
something like:

  -----BEGIN PGP MESSAGE-----
  Version: PGP 8.0.2 - not licensed for commercial use:
  www.pgp.com

  qANQR1DBw04Dxrpn2akpjMkQD/457fxRygbnZG7jAssMb4JuMeXqZdXmMhcGetrm
  ...
  -----END PGP MESSAGE-----

Note the "www.pgp.com" wrapped to the next line.  There isn't much you  
can do about it except check the various word-wrap settings involved.   
Some mailers are 'helpful' and break the line in two.

David