Re: WG Last Call: draft-ietf-openpgp-formats

[Jon Callas <[e-mail]>]

At 11:53 PM 6/25/98 +0100, Adam Back wrote:
   
   - Gary Howlands attack which can undetectably garble unsigned
     encrypted messages ... has this was been fixed?
   
     If not perhaps we could either fix it (include optional? unsigned
     digest inside message) or have wording added to highlight that
     unsigned encrypted messages offer little protection against garbling.

As I remember the consensus on this one, garbling is a problem on all
messaging systems unless you have a signature or a MAC. 

Adding in a MAC or digest to an encrypted packet breaks backwards
compatibility. I thought the consensus was that with 1.X we would look at
adding some form of integrity check, perhaps with a new type of encrypted
data packet.

I'm willing to add a note in security considerations. How about something
like:

Please note that encrypting an object but not signing it leaves open the
possibility that it might have been damaged (by accident or attack). If an
implementation wants to ensure the integrity of a message, it must be
signed as well as encrypted.
   
   - Is it defined that an implementation would keep processing packets
     until it gets to a terminal packet (terminal packets being
     literal packets, or the text of a clear signed message)?
   
     This is important as it allows super-encryption, and allows
     encrypted messages to contain clear signed messages (which William
     Geiger uses) plus it would be useful for experimental combinations
     people may use.
   
It is my belief that that is defined. It's implicit that an implementation
needs to keep unwrapping an object until it hits bottom, and that since a
literal packet could contain a clearsigned message, a literal should be
scanned for one. If you think a paragraph needs to be added, let us know.

	Jon



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Jon Callas                                  [e-mail]
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