[TLS] Re: Review of draft-ietf-tls-openpgp-keys-08

Simon Josefsson <jas@extundo.com> Tue, 16 May 2006 13:53 UTC

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From: Simon Josefsson <jas@extundo.com>
To: <Pasi.Eronen@nokia.com>
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Date: Tue, 16 May 2006 15:53:39 +0200
In-Reply-To: <B356D8F434D20B40A8CEDAEC305A1F2402A799DB@esebe105.NOE.Nokia.com> (Pasi Eronen's message of "Tue, 16 May 2006 14:59:38 +0300")
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Cc: tls-bounces@lists.ietf.org, tls@ietf.org
Subject: [TLS] Re: Review of draft-ietf-tls-openpgp-keys-08
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<Pasi.Eronen@nokia.com> writes:

> Nikos Mavrogiannopoulos wrote:
>
>> Indeed there are situations were a list might do, but there are also
>> situations where a graph would be better, or just a single one might
>> do.  The idea in this draft is to keep the key exchange separate
>> from any local verification policy.  If one wants to use the web of
>> trust, he can use it. If somebody else wants to use openpgp keys the
>> same way as PKIX certificates, he can also use the current draft.
>> In all cases unknown keys are retrieved via a key server or by other
>> means.
>
> This argument would also suggest that the ability to send multiple
> X.509 certificates is unnecessary, since all the other certs could
> (in theory at least) be retrieved from directory servers. 
>
> You can't use this draft "the same way as PKIX certificates" unless
> you have the key server or "other means" working in practice.

I believe PGP key servers are working in practice.

> In current uses of TLS with X.509 certificates, this infrastructure
> is not necessarily present, and the ability to send several
> certificates is used.
>
> Thus, I would not hard-code this limitation in the specification,
> especially when it's very easy to avoid (just allow a list just
> as in normal TLS), and there's just 3 bytes of overhead for 
> implementations that send only one PGP key... (and in fact
> even this overhead could be avoided if we remove the redundant
> length field by stating that the "key descriptor type" is the
> first byte of the key data)

I'd disagree that it is that simple to fix that: If the draft permit
more than one key, I believe it has to describe how implementations
are supposed to use more than one key to build the chain, or at least
mandate some specific behaviour.

I agree that limiting the protocol to carry one key is a theoretic
limitation, although I don't see anyone describing a practical
scenario where this limitation is critical.

Regards,
Simon

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