Cryptography Reference
In-Depth Information
Figure 4.11:
The
Copacobana
DES
cracking
machine
(from
www.
copacobana.org
, Gallery, with the courtesy of the authors).
read quite often:
DES is not secure against national intelligence agencies and
large organizations
. I tend to rewrite this sentence to read:
Don't use DES for encryption if a party interested in the plaintext would be
willing to pay a three-figure or four-figure sum. (The money amounts estimated
really include all 'expenses'; otherwise we would have to speak of a two-figure
sum.)
Nobody doubts that the key length of 56 bits instead of 128 bits came about at
the request of the NSA. We can guess why. However, this corresponded to the
situation in place 20 years ago! There is much speculation as to whether and
how the NSA cracks DES. Rumors have it that the NSA disposes of devices
the size of small suitcases that handle such tasks in a matter of seconds.
Alternative Methods
With everything said above, we could actually shelve the 'DES cryptanalysis'
topic. A real vulnerability hasn't been found to this day; all that remains is
brute force, and this is something that can be done today. All other attempts
at breaking DES merely promoted the theory, and were practically unusable.
But the theory is decisive in evaluating new algorithms with slightly larger key
lengths, where brute force won't do the trick. For this reason, we'll stay with
this topic a bit longer.
For example, it would be possible to use very large optical memories with
values computed in advance. In the 'simplest' case, an attacker would have to
