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Re: [kitten] GSS-only enctypes

Nico Williams <nico@cryptonector.com> Wed, 01 April 2015 21:05 UTC

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Date: Wed, 01 Apr 2015 16:05:53 -0500
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From: Nico Williams <nico@cryptonector.com>
To: Greg Hudson <ghudson@mit.edu>
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Subject: Re: [kitten] GSS-only enctypes
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On Wed, Apr 1, 2015 at 4:00 PM, Greg Hudson <ghudson@mit.edu> wrote:
> On 04/01/2015 04:04 PM, Benjamin Kaduk wrote:
>> I'm not sure that we got enough active input at the meeting on this
>> question to be able to declare consensus.  Regardless, we should ask the
>> list if there are objections to (or support for) using the Kerberos
>> enctype number space for enctypes with restricted usability (i.e., only
>> for subsession keys, or GSS, etc.).
>
> I didn't totally understand all of Nico's reasoning about this when he
> spoke at the meeting.  In general I think it's fine; it lets us
> negotiate AEAD enctypes using RFC 4537 enctype negotation and the
> existing subkey fields when mutual auth is used.

Conversely, not reusing the RFC3961 enctype namespace means a) adding
a new extension like RFC4537 to carry the client's/initiator's AEAD
enctype list and sub-keys, b) extending AP-REP to carry the
server's/acceptor's sub-key and choice of AEAD enctype.  That seems
like lots of unnecessary complexity.

That's my reasoning.

Nico
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