Date: Wed, 6 Jul 2022 15:01:19 -0400 From: Demi Marie Obenour <demi@...isiblethingslab.com> To: oss-security@...ts.openwall.com Subject: Re: Re: DO NOT OPEN PREVIOUS MAIL Re: Denial of service in GnuPG On Wed, Jul 06, 2022 at 04:50:11PM +0200, Solar Designer wrote: > On Wed, Jul 06, 2022 at 09:47:28AM -0400, Demi Marie Obenour wrote: > > On Wed, Jul 06, 2022 at 03:38:10PM +0200, Solar Designer wrote: > > > On Wed, Jul 06, 2022 at 07:02:59AM -0400, Demi Marie Obenour wrote: > > > > Was adding compression to PGP even a good idea in the first place? > > > > > > I think actually yes, it was, especially back then. It has probably > > > helped more than it hurt in PGP's lifetime so far. > > > > Interesting. Why do you say that? > > Oh, I didn't feel this even needed explanation, and I feel silly writing > the below and don't really have time for it (lesson re-learned: should > have stayed silent), but well. > > PGP is commonly used on compressible data (such as text), and PGP > messages are then transferred over a network and finally stay in > people's mailboxes or such. Bandwidth was commonly low back then, and > storage much more limited than today's. > > Some compression existed for unencrypted messages - some network links > somewhat compressed (e.g., V.42bis), some mail clients supported mailbox > compression, and of course a mailbox could also be compressed manually. > > Obviously, already encrypted content is not compressible. > > Without built-in compression in PGP, its messages would be slower to > transfer and larger to store. Compression would need to be performed > before PGP, which would be an inconvenience and would lead to similar > risks, especially if automated, and would often not be done. In PGP, > it's just one standard way to do it, not more than one. > > So compression was of some benefit to a lot of people. We could argue > that it's little benefit, but multiplied by the number of people it's > significant. Was compression also a problem for a lot of people? > Theoretically, yes, but in practice those attacks were not common. > > We could also argue that PGP never became popular, MUA integrations are > poor, etc., and as a consequence that its individual features were not > of a lot of benefit to computer users at large. While true, that > argument also means the risks associated with those features did not > apply to most computer users. So it's irrelevant. > > What I say is that for the geeks using PGP, compression was overall of > more benefit than risk. > > Oh, and I'm also grateful for compression in SSH, despite of my own > criticism of its effect on security. > > Alexander Thanks! I had not considered this at all, and it makes a ton of sense. Being able to compress data prior to encryption is indeed necessary if one wants to avoid using more space than a message compressed using normal methods. -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)
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