I was not referring to post-encryption compression in the context of SSL or
other, proven, known-sane encryption algorithms.  I probably should have
made this point *much* clearer to avoid confusion.  I posed the scenario to
would-be cryptographers who [99.99999% of the time] wrongly believe they've
created the "next great encryption algorithm".

In any case, the Apache processing chain applies SSL as the last stage
anyway, so compressing *after* encryption, under normal Apache request
processing, won't happen without someone [who knows *exactly* what they're
doing] forcing the issue.

Best~
-dsp

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Eric Rescorla
Sent: Wednesday, August 20, 2003 11:44 AM
To: [EMAIL PROTECTED]
Subject: Re: configuration question


Cliff Woolley <[EMAIL PROTECTED]> writes:

> On Tue, 19 Aug 2003, Eric Rescorla wrote:
>
> > "Dave Paris" <[EMAIL PROTECTED]> writes:
> > > In addition to Owen's salient points about compression working
efficiently
> > > on repetitive strings in plaintext/binary data (e.g. whitespace in a
Word
> > > document) and not on random data (e.g. encrypted data), some
encryption
> > > algorithms can actually be weakened by compressing the resulting data,
> > > giving a cryptanalyzer clues to the inner workings of the algorithm.
> >
> > No reasonable encryption algorithm will be weakened this way.
>
> I agree.  I'm guessing what he meant is that some encryption algorithms
> are weakened if their /input/ is pre-compressed by some known algorithm.
> If the cleartext is in some known format, it might possibly be easier to
> recover it from the ciphertext.

True. But no modern algorithm is susceptible to this kind of known
plaintext attack either. Moreover, SSL incorporates all sorts of
opportunities for known plaintext. I wouldn't worry about this one.

-Ekr
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