[openpgp] Padding packets

[Werner Koch <[e-mail]>]

Hi!

The idea of a padding packet is in general a good idea and has been
discussed many times:

   5.14.  Padding Packet (Tag 21)

   The Padding packet contains random data, and can be used to defend
   against traffic analysis (see Section 14.10) on version 2 SEIPD
   [...]
   Its contents SHOULD be random octets to make the length obfuscation
   it provides more robust even when compressed.

The problem with random padding packets is that this opens a high
capacity channel with all its problems.  Having this in the protocol is
a problem because applications taking care not to leak too much
information will need to reject such messages and inform the user about
a possible problem.

Please drop this.  A better mechanism to add padding is by handling this
at the MIME layer.  In any case, a well defined pseudo-random generator
is required.

At this opportunity I checked the Literal Data packet and unfortunately
noticed that not only the 'u' has gone but also the 'm' which we
introduced to declare MIME content to avoid relying on heuristics.  That
these flags are not included in the signed material is not a problem,
because they are only hints to the implementation.


Salam-Shalom,

   Werner


-- 
The pioneers of a warless world are the youth that
refuse military service.             - A. Einstein