On Jan 13, 2011, at 2:41 AM, Charles Lindsey wrote:
On Wed, 12 Jan 2011 17:10:52 -0000, Dave CROCKER
<dhc(_at_)dcrocker(_dot_)net> wrote:
This raise a specific and interesting technical point. I haven't seen a
response so far, so...
The core of this technology has keys that are named and accessed in
terms of
domain names. It really is fundamental to this technical approach.
I don't see how that can be so.
The fundamental core of this technology is a mechanism for contructing a
hash covering a named selection of headers and a body, coupled with some
canonicalization rules, and incorporating that into a signature header
using some well-known algorithm such as rsa (but allowing for others).
The question of making the public key available is entirely orthogonal to
that core protocol. The DSN mechanism is fine for some applications,
especially where the lifetime of the signature is at most a few weeks. But
other means of publicising (and especially of authenticating) public keys
are also in widespread current use and there is nothing in the core
protocol that would prevent their use in other applications where they
were more suitable.
But if other ways of getting the public key are more suitable, what's
left? The only thing DKIM does is allow a domain to assert responsibility
for a message in a relatively cheap (if unreliable) way.
If you take away the fundamental "You use this selector and this d=
value in order to find the public key" then you're not left with much other than
a quick-and-dirty canonicalization method that's tuned to the ways messages
get corrupted in email transit.
If someone wants to assert that the content of a message hasn't
changed, and they're not dealing with the weird, very email-specific,
constraints
that DKIM is under (transparency to non-DKIM aware recipients, random
body alterations en-route) then DKIM seems a fairly poor way of doing
that, and there are several "real" public-key signing approaches that might
better suited.
So DOSETA should provide for multiple plug-in key storage mechanisms in
just the same was as it provides for multiple plug-in canonicalizations.
By all means include the current DNS method as plug-in-key-management #1.
What would be a good use case for DKIM-without-DNS?
Cheers,
Steve
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