Mailing List Archive

WKD: conveying intent of encrypt-by-default?
Folks,

I setup WKD for work a while back, to publish the PGP keys for those who
had them. Then in November I removed the first key because it was
causing Protonmail users to keep sending encrypted to the recipient and
a lot of his communications turned out to be with Protonmail users.

Now we've had this happening again, with someone else, and one very
plausible outcome at this point is that we remove almost everyones' keys
from WKD, leaving only those who sign security advisories, because WKD
and the ecosystem right now is causing bigger problems than it solves.

I think that there's a perfectly reasonable conflation of semantic
intent. I'm not sure what the solution is, although I'm thinking that
_perhaps_ the answer is to extend the allowed values in the "policy"
file, to convey intent to a different audience than those uploading
keys.

Problem: we use PGP for signing and for certain transactions which need
high confidentiality, but for the most part, for most of our staff,
setting up a PGP-capable mail client with our mail-provider is a pain
and we're not interested. We want the PGP keys _available_ for people
to have a trusted path to the key, but that does _not_ mean that we want
people to default to using PGP for all communications with us.

While Protonmail is the triggering party here, I don't think that
they're at fault: for their model, what they've set up is probably a
reasonable implementation. So please, no rants about Protonmail.

Am I right in thinking that WKD was not really intended to be a trigger
for opportunistic upgrade to PGP-encryption for messaging?

Does it seem reasonable to add a directive to WELLKNOWN/policy, so that
any WKD client can see what a general domain policy is?

I could see individual users having other preferences, and I guess
there's no reason that an additional binary PGP packet, not signed by
the key, couldn't be served up together with the key from the WKD
server. But that's more extensive coding to handle and interpret.

Tentatively, perhaps:

email-encrypt-by-default: yes
email-encrypt-by-default: no

and then if not present, then the intent is unspecified. We would then
add "email-encrypt-by-default: no" and then the WKD draft could clarify
as an implementation consideration that "availability of the key does
not imply routine use of the key is desired".

-Phil
Re: WKD: conveying intent of encrypt-by-default? [ In reply to ]
Phil Pennock via Gnupg-users wrote:
> [...]
>
> Problem: we use PGP for signing and for certain transactions which need
> high confidentiality, but for the most part, for most of our staff,
> setting up a PGP-capable mail client with our mail-provider is a pain
> and we're not interested. We want the PGP keys _available_ for people
> to have a trusted path to the key, but that does _not_ mean that we want
> people to default to using PGP for all communications with us.
>

Simple option if most users at your site will be generating PGP
signatures but not running PGP-capable MUAs: generate sign-only keys
and put those in WKD. You would need a second mechanism for
distributing the encryption-permitted keys for those users who need
them, but the encryption keys could in turn be signed with the WKD
sign-only keys to prevent a man-in-the-middle attack.


-- Jacob

_______________________________________________
Gnupg-users mailing list
Gnupg-users@gnupg.org
https://lists.gnupg.org/mailman/listinfo/gnupg-users
Re: WKD: conveying intent of encrypt-by-default? [ In reply to ]
On Mon, 3 Oct 2022, Phil Pennock via Gnupg-users wrote:

> Folks,
>
> I setup WKD for work a while back, to publish the PGP keys for those who
> had them. Then in November I removed the first key because it was
> causing Protonmail users to keep sending encrypted to the recipient and
> a lot of his communications turned out to be with Protonmail users.
>
> Now we've had this happening again, with someone else, and one very
> plausible outcome at this point is that we remove almost everyones' keys
> from WKD, leaving only those who sign security advisories, because WKD
> and the ecosystem right now is causing bigger problems than it solves.
>
> I think that there's a perfectly reasonable conflation of semantic
> intent. I'm not sure what the solution is, although I'm thinking that
> _perhaps_ the answer is to extend the allowed values in the "policy"
> file, to convey intent to a different audience than those uploading
> keys.
>
> Problem: we use PGP for signing and for certain transactions which need
> high confidentiality, but for the most part, for most of our staff,
> setting up a PGP-capable mail client with our mail-provider is a pain
> and we're not interested. We want the PGP keys _available_ for people
> to have a trusted path to the key, but that does _not_ mean that we want
> people to default to using PGP for all communications with us.
>
> While Protonmail is the triggering party here, I don't think that
> they're at fault: for their model, what they've set up is probably a
> reasonable implementation. So please, no rants about Protonmail.
>
> Am I right in thinking that WKD was not really intended to be a trigger
> for opportunistic upgrade to PGP-encryption for messaging?
>
> Does it seem reasonable to add a directive to WELLKNOWN/policy, so that
> any WKD client can see what a general domain policy is?
>
> I could see individual users having other preferences, and I guess
> there's no reason that an additional binary PGP packet, not signed by
> the key, couldn't be served up together with the key from the WKD
> server. But that's more extensive coding to handle and interpret.
>
> Tentatively, perhaps:
>
> email-encrypt-by-default: yes
> email-encrypt-by-default: no
>
> and then if not present, then the intent is unspecified. We would then
> add "email-encrypt-by-default: no" and then the WKD draft could clarify
> as an implementation consideration that "availability of the key does
> not imply routine use of the key is desired".
>
> -Phil
>

Hi Phil,

ignoring your proposal (it sounds valid to me), would it be an option to
make the key a pure signing key? What's the use case to have an encryption
key but not receive encrypted email by default?

regards,
Erich


_______________________________________________
Gnupg-users mailing list
Gnupg-users@gnupg.org
https://lists.gnupg.org/mailman/listinfo/gnupg-users
Re: WKD: conveying intent of encrypt-by-default? [ In reply to ]
Hi Phil,

To clarify: Why do you put keys intended only for signing into the WKD?
The only purpose of the WKD is to discover keys used to encrypt outgoing
data/mail. To verify a signature the WKD does not really help because
there is no way to look up the key by fingerprint. Well, one of the
fallbacks is:

/* If the above methods didn't work, our next try is to retrieve the
* key from the WKD. This requires that WKD is in the AKL and the
* Signer's UID is in the signature. */

However, to be able to do this, the signer needs to specify the signing
key by NAME (e.g. wk@gnupg.org) and not key fingerprint or keyid (e.g.
AEA84EDCF01AD86C4701C85C63113AE866587D0A) as suggested. Or to use the
--sender option.

Is this your use-case? Makes some sense to me. Summary of options:

1. Upload sign-only keys (strip the encryption subkey). You can't use
the Web Key Service in this case. You have to resort to another
mechanism like build a local mirror and rsync it.

2. Add a notation to the key not to use the encryption key without
asking. This requires all clients to understand this notation and
act acordingly.

3. Add a WKD policy not to use the key for opportunistic encryption.
Also needs cleint changes.

4. A variant of 1 which strips the encryption subkey after the
publication has been confirmed. This can be done with a WKS protocol
extension. Advantage is that it can be done on a key by key base.



Salam-Shalom,

Werner

--
The pioneers of a warless world are the youth that
refuse military service. - A. Einstein
Re: WKD: conveying intent of encrypt-by-default? [ In reply to ]
On 2022-10-04 at 20:00 -0400, Daniel Kahn Gillmor wrote:
> Autocrypt's focus is ubiquitous deployment of keying material (in the
> form of OpenPGP certificates) so that people *can* encrypt when sending
> mail. We found that one of the big risks is that a peer might
> *automatically* encrypt when a cert is available, which becomes
> burdensome for a user who does not have the ability to easily decrypt
> messages. We don't want burdened users to stop distributing their cert
> entirely because of this annoyance or frustration.

This.

> Getting clients to respect this setting if published in WKD (or that the
> lack of it means "do not encrypt by default") is an entirely different
> subject, of course. And i know you said "no Protonmail rants" so i
> won't call them out specifically here, but MUA developers generally
> really do need to take the ecosystem effects of their choices seriously.
> Any MUA that promiscuously encrypts *by default* to someone who has not
> clearly indicated that they are comfortable with every inbound message
> being encrypted is inviting that user to see encrypted e-mail as a
> hindrance and an annoyance. That's not a great way to spread the
> capability of people actually being able to use encrypted mail when it
> matters, or to help people through a process of gradual adoption.

Exactly this. We need encryption _available_, but culturally
"encrypt-by-default" is not going to fly.

Almost all email usage locally is Gmail, with the browser app or the
official Gmail mobile apps. That is not going to change.

We have to have a sensible means of key discovery for exchanging
encrypted mail _when the situation warrants it_, such as distributing
sensitive data or receiving security reports. This is not about
signing. This is about using encrypted content being a PITA for most
people.

The clients encrypting all mail by default are killing the use of
OpenPGP and MIME-integrated PGP-encrypted email locally. It's another
hammer in the coffin-lid of PGP's reputation as a reasonable technical
solution for the problem spaces we care about.

It is not hyperbole to say that this one issue has done more to drive
the use of "age" encryption (with copy/paste into and out of emails as
intact ASCII-armored blobs) than anything else. And age armored
ciphertext pasted into Slack. It might seem clunky, but it works
reliably and it aligns with cultural expectation of "only use this for
things which really need the protection, otherwise just rely upon TLS
and professional service operators". TLS for SMTP is not end-to-end,
but it turns out to be "good enough" for most daily usage, particularly
within a domain or with a few business partners.

-Phil

_______________________________________________
Gnupg-users mailing list
Gnupg-users@gnupg.org
https://lists.gnupg.org/mailman/listinfo/gnupg-users
Re: WKD: conveying intent of encrypt-by-default? [ In reply to ]
Hello


> Getting clients to respect this setting if published in WKD (or that the
> lack of it means "do not encrypt by default") is an entirely different
> subject, of course. And i know you said "no Protonmail rants" so i
> won't call them out specifically here, but MUA developers generally
> really do need to take the ecosystem effects of their choices seriously.
> Any MUA that promiscuously encrypts *by default* to someone who has not
> clearly indicated that they are comfortable with every inbound message
> being encrypted is inviting that user to see encrypted e-mail as a
> hindrance and an annoyance. That's not a great way to spread the
> capability of people actually being able to use encrypted mail when it
> matters, or to help people through a process of gradual adoption.

Yes, I use protonmail, beside others. I opened an testaccount with
mailbox.org, which offers you to encrypt all incoming messages with your
public key if you specify it in the settings with their
no-reply@mailbox.org private key.

I have also tutanota, as it offers easily to send encrypted emails
through an agreed password.
Still searching the best way to go where I have all sent emails
encrypted locally as well even they the mail to the receiver can't be
encrypted.

At which point are you willing to compromise? If course it is not ideal
if proton has even the private key even without entering a passphrase
for it. But they do it with the intention to get more encrypted mails on
the transport.

Oh dear I should meet you guys and discuss in person. Many questions
around, I certainly do not best-practice but take it more and more
easier this topic.

If I allow mailbox.org to encrypt all my messages then i do so
intentionally. protonmails are encrypted too, but I always see them
cleartext as the pgp-stuff as handled in the background unknowingly to
the user.


> We have to have a sensible means of key discovery for exchanging
> encrypted mail _when the situation warrants it_, such as distributing
> sensitive data or receiving security reports. This is not about
> signing. This is about using encrypted content being a PITA for most
> people.

Thunderbird has an autodiscovery feature to search for public keys.


> It is not hyperbole to say that this one issue has done more to drive
> and professional service operators". TLS for SMTP is not end-to-end,
> but it turns out to be "good enough" for most daily usage, particularly
> within a domain or with a few business partners.

I just had cryptography in my bachelor and the teacher said the way to
go is not TLS between servers as the mails still could be read. And that
it's likely not gonna be implemented. Yes, right in the sense as the
mail still can be read on the mailserver, but it would still help so
they can't just get read. But first the servers should shut down
TLS1.0/1.1; still too many with that protocol around.


My two cents..



_______________________________________________
Gnupg-users mailing list
Gnupg-users@gnupg.org
https://lists.gnupg.org/mailman/listinfo/gnupg-users