Subject: Re: [openpgp] Clarifiction on v5 signatures

From: Heiko Stamer <[email-masked]>
Date: Sun, 11 Nov 2018 13:57:12 +0100

Hey Wiktor,

Am 26.10.18 um 13:19 schrieb Wiktor Kwapisiewicz:

> Split key (0x10) looks like a good way to implement separation of duties
> (where multiple people are needed to use the key). I don't think this is
> possible in OpenPGP now.

This was one reason to create DKGPG: https://www.nongnu.org/dkgpg/

Currently, there are some efforts at NIST on threshold cryptography:
https://csrc.nist.gov/projects/threshold-cryptography

Best regards,
Heiko.

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From: Wiktor Kwapisiewicz <[email-masked]>
Date: Sun, 11 Nov 2018 22:08:15 +0100

Hi Heiko,

> https://csrc.nist.gov/projects/threshold-cryptography

That's intriguing, thanks for bringing this up, I'll definitely check this out
as this is something I've been thinking of for quite some time.

Kind regards,
Wiktor

-- 
https://metacode.biz/@wiktor

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From: Werner Koch <[email-masked]>
Date: Tue, 13 Nov 2018 16:06:35 +0100

On Fri, 26 Oct 2018 15:42, [email-masked] said:

> 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.

Because they might not be intended for encryption of mail or the keys
are offline etc.  Further if you use wildcards extra encryption subkeys
are extra annoying.

>> 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 threat model which can be mitigated by having different private
subkeys on each device.  The problem is that you want to read the mails
on every device and thus the sender needs to encrypt it to all subkeys.
The compromise of a single device and its subkey will anyway compromise
all your mails encrypted to that set of subkeys.  Thus my conclusion is
copying the private key onto all device is much easier.

Shalom-Salam,

   Werner

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