Partial length headers

Hasnain Mujtaba hmujtaba at
Mon Nov 24 17:40:39 CET 2003

Thank you for the replies David. I am trying to implement partial length
encoding in Java. I want to study how GPG does it. If you could point me
to the relevant source files, I would be most grateful. 


-----Original Message-----
From: gnupg-users-bounces at
[mailto:gnupg-users-bounces at] On Behalf Of David Shaw
Sent: Monday, November 24, 2003 1:30 PM
To: gnupg-users at
Subject: Re: Partial length headers

On Fri, Nov 21, 2003 at 08:16:20PM -0500, Hasnain Mujtaba wrote:
> Thanks. A couple more questions:
> Looking at the pgpdump of an encrypted file, I see that GPG uses the
> Symmetrically Encrypted and MDC Packet (tag 18). 
> I cannot find this tag in RFC 2440. Where can I get more information
> this tag type and its internal structure? I am trying to understand
> partial length chunks are built. Are these partial chunks nested
> the outer Symm Encrypted and MDC Packet? What is the name of the
> outer-most packet? Is it the Symmetrically Encrypted packet? 

The MDC packet is defined in 2440bis - the draft that will eventually
replace RFC-2440.  You can get the latest draft at


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