Re: [openpgp] Clarifiction on v5 signatures

[Paul Fawkesley <[e-mail]>]

Hi folks,

> 
> AFAIK, OpenKeychain encrypts to all non-expired subkeys.  I think this a
> bit to course of an action.  For example if a subkey has been created
> with future timestamp to help with key rollover.  Thus the idea to
> explicitly mark suitable subkeys.

I feel OpenKeychain's approach here is sensible. Less complexity is
better: it's a huge burden on implementors to support yet-another-flag.

If a key has multiple valid encryption subkeys, it's advertising that
it's OK to pick *any* of those subkeys. That's pretty arbitrary. I don't
see why picking *all* would be any worse than picking an arbitrary one.

> The ADSK (Additional Decryption Subkey) is an idea of mine on how to
> ease ease encryption to several devices.  You would install the separate
> private subkeys on each device and if the sender supports the ADSK it
> would encrypt to these subkeys.  This is similar to what OpenKeychain
> does but a more selective approach.  OTOH, I am not sure whether one can
> find a threat model where such a scheme would be useful.

Not sure I understand what you mean about threat model here?

A team I previously worked in abandoned email encryption altogether
because they couldn't access emails on their phones.

Now they use unencrypted email - is that the sort of threat model you
were thinking of?

Paul