Contents
What is a Web Key Directory?
A Web Key Directory (WKD) provides an easy way to provide and get the current public key for a given email address through HTTPS. Thus it is infrastructure to improve the user experience for exchanging secure emails and files.
Because the email address is needed to ask for a public key, using a Web Key Directory preserves the privacy of this address. If a public key is found, it can be used to encrypt to the email address right away.
for Users
How does an email client use WKD?
- A user selects a recipient for an email.
- The email client uses the domain part of the email address to construct which server to ask.
- HTTPS is used to get the current public key.
- The email client is ready to encrypt and send now.
An example: https://intevation.de/.well-known/openpgpkey/hu/it5sewh54rxz33fwmr8u6dy4bbz8itz4?l=bernhard.reiter is the direct method URL for "bernhard.reiter@intevation.de".
gpg-wks-client command can be used to generate wkd hash or wkd url for any email address, though it seems to prefer the subdomain method url over direct url.
$ gpg-wks-client --print-wkd-hash bernhard.reiter@intevation.de it5sewh54rxz33fwmr8u6dy4bbz8itz4 bernhard.reiter@intevation.de
$ gpg-wks-client --print-wkd-url bernhard.reiter@intevation.de https://openpgpkey.intevation.de/.well-known/openpgpkey/intevation.de/hu/it5sewh54rxz33fwmr8u6dy4bbz8itz4?l=bernhard.reiter
What does it mean for users?
A user just selects the recipients of a message and by default the encryption state of that mail will toggle if encryption keys can be found for all of them.
For a basic level of security the user does not need to check a fingerprint or do any key management manually.
How to set it up?
If you want to set up a Web Key Directory for your own server or your own server you only need access to a webserver for your domain. See: WKDHosting
For a larger organization it is recommended to set up a complete Web Key Service, which will help to automate Web Key Directory publishing.
Stopgap method - temporary central keyserver
Not recommended - but a temporary workaround - is to use "WKDaaS" and delegate delivery of your pubkey to a central service. Doing this you'll expose all people that want to use crypto when communication with you towards another party of the central service or monitoring the central service. This third party can then see the communication pattern.
However this maybe a temporary solution until you will convince your mail provider to enable at least the WKD serving part or to switch to a more privacy aware mail provider.
One service is keys.openpgp.org, where you can set the CNAME record of the "openpgpkey" subdomainto "wkd.keys.openpgp.org" the CNAME entry should look like this.
openpgpkey.example.org. 300 IN CNAME wkd.keys.openpgp.org.
In addition you need to register your pubkey with them.
Other drawbacks:
- As any WKD service, they'll be able to serve a different pubkey to some domains at some time, however opposed to your email provider you do not have a contractual relationship with them.
- Elder GnuPGs like the some on Debian Stretch do not offer the necessary modern WKD implementation for a successful request, so you are reaching less communication partners with this compared to real WKD.
- (For the overall ecosystem, we need more decentral services instead, it is at the core of OpenPGP security promise. So you are missing to set a good example. ;) )
Web Key Directory (WKD) / Web Key Service (WKS) what is the difference?
The Web Key Directory is the HTTPS directory from which keys can be fetched.
The Web Key Service is a tool / protocol to automatically publish and update keys in the Web Key Directory. It is optional to reduce the administrative effort of a Web Key Directory.
Documentation how to set up a Web Key Service can be found on the Web Key Service page.
Technical Details
You can find the concepts / technical details under WKDDetails.
Trust and security considerations are outlined as part of the AutomatedEncryption concept.
Troubleshooting
If you have arrived here after receiving an email saying:
The web page
https://gnupg.org/faq/wkd.html
explains how you can process this message anyway in
a few manual steps.you can find further instructions at WKSManualConfirmation.
Implementations
GnuPG
- WKD lookup is implemented in GnuPG since v2.1.12. It is enabled by default since 2.1.23..
- WKS server and client tools are part of GnuPG since v2.1.14
Mail Clients
Any mail client which uses the --locate-keys option of GnuPG will automatically do WKD requests.
Known mail clients with WKD Support:
- Desktop:
- Thunderbird/Enigmail 2.0
- KMail since Version 5.6
- Outlook with GpgOL since Version 2.2.0
- Claws Mail since 3.18.0 / 4.0.0
- Balsa has no official release - which is supporting WKD - yet but the feature was merged into the main branch
- Browser-Extensions:
- Mailvelope since Version 3.0.0 (Dez 2018)
- Android:
- K9Mail with OpenKeyChain since Version 5.1 (Jun 2018)
- FairEmail with OpenKeyChain since OpenKeyChain 5.4 (FAQ, (12) How does encryption/decryption work?)
Progress of WKD in different mail clients
Known mail clients with WKS Support:
- Thunderbird/Enigmail 2.0
- KMail since Version 5.6
- Outlook with GpgOL (basic, pre-release) since Version 2.2.1 asyGpg2016)
Self-hosted email setups offering WKD + WKS:
- caesonia - OpenBSD email service.
- Excision Mail - OpenBSD email service using ansible: Has multiple-domain WKS support.
- Userli - Web application to (self-) manage e-mail users and encrypt their mailboxes..
Mail Service Providers offering WKD
- Forward Email has WKD support for inbound, outbound, and forwarded mail. (Since 2023-12-27)
- Posteo offers web key directory lookup and service for @posteo.de-addresses (Since 2016-12)
- Protonmail supports web key directory lookup (Since 2018-11) in both ways.
- netzguerilla offers web key directory lookup. (Since 2017-10-11)
- systemli.org offers web key directory lookup and service for all hosted domains (Since 2020-10-15)
- mailbox.org claims to offer web key directory lookup
- See announcement https://mailbox.org/en/post/the-keyserver-is-dead-long-live-the-keyserver 2019
- In the forum in 2021 a question (German) was asked when WKD would be offered. The thread was deleted but you can find it via the Internet Archive: https://web.archive.org/web/20211019060747/https://userforum.mailbox.org/topic/wann-wird-ein-web-key-directory-wkd-angeboten
- At least the OpenPGP key for the privacy mail address of mailbox.org can be found via:
- The command gpg-wks-client --with-colons --supported mailbox.org also gives a positive result
- mail.de maintains a WKD server (Screenshot: attachment:mailde_wkd.png)
- Mailfence supports web key directory lookup (Since 2021-11-18) in both ways.
Organizations using WKD
- C3S
- Credativ GmbH, DE
- debian.org
- gentoo.org
- gnupg.org (Testing accounts available for developers implementing WKD in MUAs.)
- KDAB.com
- kernel.org
- Nikka Systems
- occrp.org
- torproject.org
- f-droid.org
- guardianproject.info
- privacyguides.org
- Univention GmbH
- (Several unlisted organisations. And of course the main designers of WKD - g10code.com, intevation.de.)
(Add yourself or let us know if you want to be publicly listed.)