Dan Brown - Digital Fortress book

[vedaal at hush.com]

>Message: 1
>Date: Wed, 14 Jan 2009 11:47:58 -0500
>From: "Robert J. Hansen" <rjh at sixdemonbag.org>
>Subject: Re: Dan Brown - Digital Fortress book

>The TRANSLATR machine does not work and cannot work, not under the 
>laws of physics as we know them to be.


ok,
granted,

as well as the inaccurate crypto of the 'uncrackable' cipher,


but it does raise a fascinating question:

"assuming a brute force attack is feasible in real time,
how could one design a cipher that is invulnerable to  brute force 
attack
(other than an OTP )?"


as a general possibility:

(1) [as explained in the Digital Fortress book]
what if the decryption program didn't know when it had successfully 
decrypted ...

(a) change the ciphertext, and let the brute force machine merrily 
try to crack the wrong ciphertext ...
(re-encrypt the ciphertext with another random session key,
then if the brute force attack tries all possible ciphertexts to 
find which one is the right one,
it sort-of becomes similar to attacking an OTP, in that the brute 
force decryption would yield several plaintexts of contradictory 
information

in practice, though,
the attacking program could just brute force the keyspace of the re-
encrypted ciphertext, 
until it would get a ciphertext that would decrypt to a real 
plaintext,
so,
unless there is a way to re-encrypt the ciphertext in a way that it 
could produce multiple different plaintexts when using different 
session keys, it wouldn't work

anyway,
for me,
the book presented interesting crypto concepts that would be 
fascinating if explored ...


vedaal

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