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RE: On shared keys (was RE: SOI: identity protection and DOS)
Yes I agree that the symmetric key adds more secure delivery requirement,
although the delivery scalability is the same as that of a pre-shared public
key system. In a managed IPsec VPN system, usually there is a dedicated
security channel between the managed device and the server. So to such a
type of provisioning and management system, the extra security requirement
imposed by symmetric key is non-significant. So I hope that we at least
agree that key delivery scalability is about the same.
-----Original Message-----
From: Sandy Harris [mailto:sandy@storm.ca]
Sent: Saturday, December 01, 2001 10:14 AM
To: 'IPsec WG'
Subject: Re: On shared keys (was RE: SOI: identity protection and DOS)
"Wang, Cliff" wrote:
>
> It depends on how you see things. I agree that you only need to have
> 2N keys in existence. But from a usage/implementation/deployment point
> of view, you are still dealing n*(n-1) key delivery. The only
> difference is that you deliver the same public key (N-1) times to N
> boxes in the case of RSA, but you deliver (N-1)*N/2 different keys in
> PSK case, assuming we are talking a full mesh relationship.
There is another important differences.
With symmetric keys, you must make all the PSK deliveries securely, whether
from peer to peer or from server to client, for the system to work.
With public key tehniques, it does not matter if the enemy learns the public
keys, so there is no need for a secure channel for those. If you have each
system generate its own public/private key pair, then only public keys ever
need to be transmitted (directly to peers or to the server if you use one)
or shared.