Re: [dns-privacy] draft-mayrhofer-edns0-padding

[Daniel Kahn Gillmor <[e-mail]>]

On Thu 2015-07-23 18:50:14 +0200, Alexander Mayrhofer wrote:

> I had a discussion with Daniel Khan Gillmor today, and we talked about
> his proposal to specify a padding option in TLS so that message-size
> based correlation attacks on encrypted DNS packets could be
> prevented. We continued discussing other options (such as "artificial"
> RRs in the additional section), and I floated the idea that we could
> use EDNS0 to include padding in DNS packets.
>
> So, I've created a quick-and-dirty strawman proposal draft for this
> idea, and i'm happy to discuss this during tomorrow's DPRIVE session
> if we have time:
>
> https://www.ietf.org/id/draft-mayrhofer-edns0-padding-00.txt

wow, thanks for the incredibly quick writeup!

I think this draft could have an informative reference to Haya Shulman's
research on difficulties in DNS encryption, which won the recent ANRP:

  https://irtf.org/anrp
  https://www.ietf.org/mail-archive/web/dns-privacy/current/pdfWqAIUmEl47.pdf

Section 3.2.2 shows that her mechanism for inferring the contents of
queries becomes *even more effective* by including the size of the
packets in her analysis.  (Everyone working on dprive should read this
paper to get a sense of some of the massive difficulties we need to
consider because of the structure of DNS traffic analysis; just
encrypting the traffic is insufficient for several reasons)

I also note that draft-mayrhofer-edns0-padding curently suggests that
the minimum padding size is 1 octet.  Is there any reason to avoid a
padding size of 0? 

        --dkg