As I wrote in my original posting, I didn't find a free copy of the
Biham paper in question.

I believe the relavant paper is titled, "How to Decrypt or Even
Substitute DES-Encrypted Messages in 2^28 Steps" in Information
Proccessing Letters 84, (2002) 117-124.

According to this paper

http://eprint.iacr.org/2002/159.pdf

by Loughran and Dowling, what the Biham paper proposes is exactly what
you wrote.

"Applying this to our attack, n=2^56 and it is only necessary to have
two collections of 2^28 ciphertexts to have a high probability of
finding a matching pair of ciphertexts."

If loughran and Dowling correctly understood Biham, then your objection
should be taken up with Biham.

The gentleman asked what the attack was, and I did my best to answer
his question correctly.

David Sexton

Unruh wrote:

Mike Amling wrote:

When opening freeme.exe I get the message: "Usage: FreeMe [-v]
protectedfile. Press to acknowledge error." Does anyone
know why it's not working? I'm running XP but have the backwards
compatibility option enabled.....

thanks,
thebaron

When reading John Savard's webpages (very well-written, imo)
on some of the historical ciphers, I found this remark ...

While the seriation step is an essential part of some
fractionation ciphers [...], using it with a digraphic
cipher has been questioned, since it allows the
cryptanalyst to pretend he is dealing with simple
substitution with 26 homophones for each letter, and
therefore may make solution easier instead of harder.

at http://www.quadibloc.com/crypto/pp1321.htm .

I don't understand how seriation followed by digraphic
substitution relates to "simple substitution with 26
homophones for each letter". (Let's ignore that the "26"
should presumably be "25" for the ciphers discussed there.)
Anyone care to explain?

Block ciphers are generally used using one of the various cryptographic
modes. Electronic Code Book, Cipher Block Chaining, Cipher Feedback,
Output Feedback, etc.

Everyone of these I've ever read about involved mixing the prior block or
a sequential constant with the plaintext, the ciphertext, or both.

I've not seen one that mixed the prior block with the key - so that each
block was encrypted with a different key. And I can think of no
particular reason that this would not work.

Have these been discussed in the literature? Are there any particular
reasons why they're not used? Less secure? Harder to prove secure?
Fashion?

Carlos Moreno wrote:

Hi Carlos.

If you mean something like DSA, I have thought about it, but I wanted
to see what to expect with RSA. Using both DSA and RSA would
complicate my system, and there is the matter of the patent dispute....

Tony Hill wrote:

Perhaps you should tell all the people working on side-channel attacks
(such as Adi Shamir (the S in RSA), and Daniel Bernstein (timing attack
against AES)) that you consider their work to be worthless? ;-þ

David Eather wrote:

but if it is known or suspected that one one the posters here did such
a thing,
and some sort of identity verification were required here,

then that poster could be traced,
(not, by you, me, or anyone here,)
but by law enforcement personnel who have the authoriity to obtain such
identifying information
from the third party certifier,
especially for a non-political universally acknowledged 'crime'

"da5id65536@yahoo.com" yahoo.com> writes:

This makes little sense unless there really are a huge number of different
keys out there.

The probability of hitting one of those keys for each external key is
2^{-28}. Since one has no guarentee that the external keys are all
different, the probability of hitting it once in n tries is
1-(1-2^{-28})^n = 1-exp(2^{-28}n). Thus n has to be at least 2^28 for this
to have any probability of success.
Ie, one would need 2^28~10^9 messages of the same header encrypted with
different keys for this to pay off once.

WEA 2007
6th International Workshop on Experimental Algorithms
http://www.dis.uniroma1.it/~wea07

June 6-9, 2007
School of Engineering
University of Rome "La Sapienza", Rome, Italy

SECOND CALL FOR PAPERS

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SUBMISSION DEADLINE: January 20, 2007
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