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Date:   Tue, 2 Aug 2022 13:16:14 -0400
From:   Konstantin Ryabitsev <konstantin@linuxfoundation.org>
To:     Bagas Sanjaya <bagasdotme@gmail.com>
Cc:     Jonathan Corbet <corbet@lwn.net>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH v1 3/5] maintainer-pgp-guide: update ECC support
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References: <20220727-docs-pgp-guide-v1-0-c48fb06cb9af@linuxfoundation.org>
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On Fri, Jul 29, 2022 at 04:11:26PM +0700, Bagas Sanjaya wrote:
> > -    If for some reason you prefer to stay with RSA subkeys, just replace
> > -    "ed25519" with "rsa2048" in the above command. Additionally, if you
> > -    plan to use a hardware device that does not support ED25519 ECC
> > -    keys, like Nitrokey Pro or a Yubikey, then you should use
> > -    "nistp256" instead or "ed25519."
> > +    Note, that if you plan to use a hardware device that does not
> > +    support ED25519 ECC keys, you should choose "nistp256" instead or
> > +    "ed25519."
> >  
> 
> nistp256 isn't just ECC key algo other than ed25519. In fact, it is a
> part of NIST curve family (the others are nistp384 and nistp521).
> 
> Maybe we can just say "If unsure, or if your hardware device does not
> support ED25519, use one of NIST curves (nistp256, nistp384, or nistp521)
> instead".

Hm... ED25519 is the default for GnuPG 2.3+, so I'm not sure it makes sense to
go into this level of detail here. Folks who are likely to need to use NIST
curves will probably already know this information without needing to list it
in this guide. As far as I can recall, TPMs and older Nitrokey Pros are some
of the few remaining devices that can't do ed25519, so the number of people
who would need to use NIST curves will likely be super small.

-K