Re: SSH resources, specifically on certificates (certificate authentication)

[Dan Ritter <dsr@randomstring.org>]

tomas@tuxteam.de wrote: 
> See, asymmetrical encryption (e.g. RSA, Elliptic Curve) is far too expensive
> to use on bulk data, so it typically is used to encrypt a key (generated on
> the spot), called "session key". The latter is used to symmetrically (e.g.
> AES) encrypt the bulk data. You use that style typically in the deferred
> case.
> 
> Perhaps there's even a security advantage in that, since the session key,
> as being used for more data gives a potential cryptanalist more material
> to chew on: then just the session key would be compromised, and you throw
> that away for the next round. I don't know.

The systems that throw it away and redo the DH exchange frequently
are said to have "perfect forward security": an attacker who gains one
session key doesn't get the next session key.

-dsr-