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Re: ssh protocol



On Sunday 23 July 95, at 14 h 45, the keyboard of Tatu Ylonen <[email protected]> wrote:

> People have also suggested using the Photuris protocol that is part of
> the IP Security work being done at IETF
> (ftp://www.cnri.reston.va.us/internet-drafts/draft-ietf-ipsec-photuris-02.txt
).
> 
> The basic idea behind the protocol goes roughly like this:
>   1. Exchange session keys using Diffie-Hellman
>   2. Each side sends a signature of the Diffie-Hellman exchange (the
>      signature can be with any of a number of algorithms; RSA and
>      Elliptic Curve systems have been defined).
> 
> If this were adapted to ssh, the protocol would look roughly like
> this:
>   1. Exchange session keys using Diffie-Hellman
>   2. Each side sends a signature of the Diffie-Hellman exchange by its
>      host key
>   3. RSA and Rhosts authentication requests would include a signature
>      by the requesting key.
> 
> This would get rid of the server key and the need to regenerate it,
> because the diffie-hellman exchange already prevents decrypting old
> conversations.  The challenge-dialogs could be avoided (unless they
> are needed for performance reasons to avoid unnecessary signature
> computations).
> 
> One could also eliminate RSA in future and start using some other
> public key cryptosystem if desired.  The Diffie-Hellman patent and the
> generic public key patent expire in 1997; the RSA-patent does not
> expire until about year 2000.
> 
> 
> Anyway, this would be a major change that probably cannot easily be
> made compatibly.  Maybe an incompatible ssh-2.x?  Anyway, I don't want
> to rush into making major changes in the protocol.
> 
> I would very much like to hear comments on this approach.
> 
>     Tatu

Stephane Bortzmeyer           Conservatoire National des Arts et Metiers
[email protected]            Laboratoire d'Informatique
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