Re: [dhcwg] DHCP hackathon in Prague: SeDHCPv6

Francis Dupont <Francis.Dupont@fdupont.fr> Wed, 07 June 2017 18:52 UTC

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From: Francis Dupont <Francis.Dupont@fdupont.fr>
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In-reply-to: Your message of Wed, 07 Jun 2017 11:10:52 -0700. <CAJE_bqeuu+fke2o7n+0O4b1MoP7KLkeF7P0p5uYv_n7kwy1C2A@mail.gmail.com>
Date: Wed, 07 Jun 2017 20:35:14 +0200
Archived-At: <https://mailarchive.ietf.org/arch/msg/dhcwg/1MQxa6g7vDF2sKrH271PxoyBYu8>
Subject: Re: [dhcwg] DHCP hackathon in Prague: SeDHCPv6
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 In your previous mail you wrote:

>  > => it is more than a fundamental issue: the idea to use RSA encryption
>  > is simply a deadly bad one...
>  
>  Could you explain it in more detail?  Is it just about the particular
>  choice of algorithm (RSA), or is it about the use of asymmetric
>  (public-key)-based encryption to encrypt DHCPv6 messages in the first
>  place?  And why is it bad?

=> in fact it is both because RSA is the only asymmetric algorithm
which provides an accepted encryption feature.
Now why it is bad (other than RSA has no future)? Just because it was
designed to protect something short as a key for a symmetric encryption
and *not* for a message with an unbound length.

>  If it's the former, (depending on the reason) we might choose a better
>  algorithm as the default/mandatory.

=> as I explained I am afraid there is no alternative which went further
than conference papers...

>  If it's the latter, we could revise the protocol so it will first
>  negotiate a symmetric session key using public-key based encryption
>  and use the session key for subsequent DHCPv6 message exchanges.  That
>  will be a quite substantial change from the current spec, but I guess
>  it's not impossible.

=> if you go to a key agreement phase followed by symmetrical encryption
I am afraid you are reinvented something which already exists so why
not investigate current possible solutions and try to use them directly?

>  > Perhaps we should drop it and restart from the beginning about
>  > address assignment security, for instance using opportunistic DNSSEC

=> oops? I wrote DNSSEC? I wanted to mean IPsec.

>  > with a client embedded first relay? At least it does not need to
>  > develop a new protocol...

Regards

Francis.Dupont@fdupont.fr