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RE: Simplifying IKE

On Tue, 14 Aug 2001, Andrew Krywaniuk wrote:
> Sorry, I meant "traffic analysis" in the more general sense of analyzing
> anything about the traffic flow, in this case specifically cryptanalysis of
> the data stream.

That's incorrect; "traffic analysis" is an idiom with a specific meaning
in the cryptography world.  Schneier, p219:

  Traffic analysis is the analysis of encrypted messages:  where they 
  come from, where they go to, how long they are, when they are sent, 
  how frequent or infrequent they are, whether they coincide with 
  outside events like meetings, and more.  A lot of good information
  is buried in that data, and a cryptanalyst will want to get his hands
  on it...

(When he says "analysis of encrypted messages", he means "without
decrypting them"; the context of this is a discussion of how traffic
analysis can assist with cryptanalysis.)

> ...Is there a well-defined term
> for this type of traffic analysis? "Data analysis"?

"Cryptanalysis" is usual.  That's a very generic term, which includes
things like chosen-plaintext attacks.

> ...a chosen-plaintext attack. If the gateway sends traffic across
> multiple SAs, then cryptanalysis of the output stream for flow A will only
> allow the attacker to crack the key for SA_A (which only protects traffic
> which was generated by the attacker).

If the encryption scheme is vulnerable to chosen-plaintext attacks, it is
already too weak to be used for protecting important data.  Well-chosen
encryption schemes are not vulnerable to (practical) chosen-plaintext
attacks, and so this argument falls apart in real life.

                                                          Henry Spencer
                                                       henry@spsystems.net
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