simultaneous symmetric and public key encryption ?

[David Shaw]

On Thu, Dec 19, 2002 at 04:34:56PM +0100, Per Tunedal wrote:
> I supposed it would be some help to Mallory to possess the plaintext when 
> attacking the encrypted text. Cf the Rosette stone used for "deciphering" 
> the hieroglyphs ...

Not really.  Modern ciphers are pretty resistant to chosen plaintext
attacks.

> 3a. Mallory gets the symmetric message key by attacking the message with 
> some help from the plain text.
> 
> 3b. Mallory attacks the encrypted session key with some help from the plain 
> session key.
> 
> 3c. Mallory gets the secret key used for encrypting the session key.

b and especially c, do not follow a.

David

-- 
   David Shaw  |  dshaw@jabberwocky.com  |  WWW http://www.jabberwocky.com/
+---------------------------------------------------------------------------+
   "There are two major products that come out of Berkeley: LSD and UNIX.
      We don't believe this to be a coincidence." - Jeremy S. Anderson