WKD for debian.org

You can now fetch the OpenPGP certificate for any Debian developer who uses an @debian.org e-mail address using Web Key Directory (WKD).

How?

With modern GnuPG, if you're interested in the OpenPGP certificate for dkg just do:

gpg --locate-keys dkg@debian.org

By default, this will show you any matching certificate that you already have in your GnuPG local keyring. But if you don't have a matching certificate already, it will fall back to using WKD.

These certificates are extracted from the debian keyring and published at https://openpgpkey.debian.org/.well-known/openpgpkey/debian.org/, as defined in the WKD spec. We intend to keep them up-to-date when ever the keyring-maint team publishes a new batch of certificates. Our tooling uses some repeated invocations of gpg to extract and build the published tree of files.

Debian is current not implementing the Web Key Directory Update Protocol (and we have no plans to do so). If you are a Debian developer and you want your OpenPGP certificate updated in WKD, please follow the normal procedures for Debian keyring maintenance like you always have.

What about other domains?

Our update here works great for e-mail addresses in the @debian.org domain, but it has no direct effect for other e-mail addresses.

However, if you have an e-mail address in a domain you control, you can publish your own WKD. If you would rather use an e-mail service in a domain managed by other people, you might also be interested in GnuPG's list of e-mail service providers that offer WKD.

Why?

The SKS keyserver network has been vulnerable to abuse for years. The recent certificate flooding attacks make fetching an OpenPGP certificate from that pool a risky operation: potentially causing a denial of service against GnuPG. In particular, anyone can flood any certificate in SKS (or other common keyservers that are not resistant to abuse).

WKD avoids the problem of certificate flooding by arbitrary third parties. It's not a guaranteed defense against flooding though: the domain controller (and whoever they authorize to update the WKD) is still capable of offering a flooded certificate via WKD. On the plus side, at least some WKD clients do aggressive filtering on certificates found via WKD, which should limit the ability of an adversary to flood a certificate in your local keyring.

Thanks

Setting this up would not have been possible without help from weasel and jcristau from the Debian System Administration team, and Noodles from the keyring-maint team.

WKD was designed and implemented by Werner Koch and the GnuPG team, in anticipation of this specific need.

Thanks to all of these people for making it possible.

What next?

There's some talk about publishing similar OpenPGP certificates in the DNS as well, using RFC 7929 (OPENPGPKEY) records, but we haven't set that up yet.