[RC5] new release candidate available.

Greg Wooledge greg at wooledge.org
Sun Nov 24 08:50:42 EST 2002

Oliver Otte (rc5list at seo.de) wrote:

> > Think about RC5-72 -- on paper it is 256 times as hard as RC5-64.
> > And it took YEARS for distributed.net to "solve" RC5-64, and all
> > that was accomplished was to decode __one__ message. 
> Don't forget we knew something about the plaintext ...

But in practice, if you're decrypting a message, you *will* know
something about the plaintext.  Otherwise, why would you know
that you want to decrypt it in the first place?

Suppose you intercept an HTTPS (HTTP over SSL) session from a web
browser and you intend to decrypt it.  You know what an HTTP session
looks like, so once you find the key, you just compare the first
few bytes of the decrypted HTTPS session against what the first
few bytes of an HTTP session should look like (e.g., "GET /" or
"POST ").

Greg Wooledge                  |   "Truth belongs to everybody."
greg at wooledge.org              |    - The Red Hot Chili Peppers
http://wooledge.org/~greg/     |
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