Re: Hand Waving vs. Rigorous Analysis... (was Security Engineering vs. Crypto Academics...)

From: Peter Gutmann (pgut001_at_cs.auckland.ac.nz)
Date: 09/07/04 

Date: 7 Sep 2004 04:18:13 GMT

"Patrick J. LoPresti" <patl@users.sourceforge.net> writes:

>For example: Instead of using one of the standard, NSA-recommended
>block cipher modes, the Kerberos designers invented their own
>("Propagating Cipher Block Chaining"). Very clever.

There was nothing else available, they had no choice.

>I seriously doubt that Biham/Shamir/etc. are going to download the
>Linux /dev/random source code and analyze it. So why not restrict
>yourself to algorithms which the experts HAVE analyzed?

Because the necessary algorithms frequently haven't been invented/analysed by
cryptographers. See "The Crypto Gardening Guide and Planting Tips",
http://www.cs.auckland.ac.nz/~pgut001/pubs/crypto_guide.txt, for more:

  There has been a great deal of difficulty experienced in getting research
  performed by cryptographers in the last decade or so (beyond basic
  algorithms such as SHA and AES) applied in practice. The reason for this is
  that cryptographers don't work on things that implementors need because it's
  not cool, and implementors don't use what cryptographers design because it's
  not useful or sufficiently aligned with real-world considerations to be
  practical.

Peter.

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