[openpgp] Deprecating compression support

[Daniel Kahn Gillmor]

On Tue 2019-03-26 09:28:19 +0100, Werner Koch wrote:
> On Sun, 24 Mar 2019 17:20, ilf at zeromail.org said:
>
>> So GnuPG development comunity: Would you be fine in changing the
>> default for new keys to "Compression: Uncompressed"?
>
> That is easy to answer: No.
>
> Removing that feature would break major use cases and deployed
> infrastructure.  The build in compression support in OpenPGP is actually
> a selling point over S/MIME.

ilf is asking about a change to the advertised preferences included in
an OpenPGP certificate generated by default with GnuPG.

Someone who wants to use the compression feature because they know
that's what they want needs only to issue a "setpref" command to
indicate that they *do* want it (if it is a "selling feature" that they
consciously care about).

This is not breakage exactly -- it's a question of where we want to push
the ecosystem.

> This can also not be done with a switch to a new key or key format
> because key management is independent from actual use.

If we were to say that v5 keys do not support in-protocol compression by
definition, then it seems like we could well do it with a switch to a
new key format.  What did you mean here?

> Please remember that OpenPGP is not only used for mail.

can you elaborate on this?  In contexts where OpenPGP is not only used
for e-mail, it's not competing with S/MIME, and it seems likely that a
simple pipeline with gzip or xz or whatever can meet the use case.

> Those who do not want to have compression, please specify that in your
> keys.  MUA authors may pass "-z0" or GPGME_ENCRYPT_NO_COMPRESS to
> disable encryption.

itym "disable compression" :)

     --dkg
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