40-bit RC5 crack meaningless??

(A gem off sci.crypt. Schwartau's mailing list is turning into the most amazing source of misinformation or disinformation about cryptography on the Net. And he's probably got the most influential audience in Washington re crypto policy. Go figure;-) ---------------- Subject: 40-bit RC5 crack meaningless?? Date: 6 Feb 1997 11:43:58 -0500 From: nobody@REPLAY.COM (Anonymous) Organization: Replay and Company UnLimited Newsgroups: sci.crypt Strassmann, the author of this denunciation of RSADS and Ian Goldberg, is the former Director of Defense Information (i.e., CIO,) of the Bush DoD and an often-insightful commentator on business culture and computing. Strange is the logic that channels the mind of the American Defense Intellectual... or, maybe he just doesn't know squat about cryptography??? (Reposted from Infowar Digest, Winn Schwartau's moderated mailing list without permission.)

Date: Thu, 30 Jan 1997 20:10:36 -0500 To: "Wright Larry" From: "Paul A. Strassmann" Subject: Further to Goldberg's Cracking Accomplishments Gentlemen:

As I suspected (see earlier private comment), the highly promoted RSA cracking contest offered a number of clues that ordinarly would not be volunteered by info-terrorists or info-criminals to IW Defense teams.

These clues made the cracking significantly easier, because it made it possible to eliminate an enormous range of possible searches.

The following was extracted verbatim from the <The RSA Data Security Secret-Key Challenge> posted on http://www.rsa.com/rsalabs/97challenge/:

Clue #1:

" ...all the RC5 contests posted as part of the RSA Secret-Key Challenge will use 12-round RC5 with a 32-bit word size. "

Clue #2:

" ...The first RC5 contest will consist of some unknown plaintext encrypted using a 40-bit key;."

Clue #3: (a giveway!)

" ... For each contest, the unknown plaintext message is preceded by three known blocks of text that contain the 24-character phrase "The unknown message is: .....".

In summary: The claim of exportable cryptography being totally insecure, because it can be cracked in 3.5 hours is not realistic. The three clues announced in the contest would not apply under infowar conditions.

What other clues may have been provided to Goldberg to support private agendas and gain shrill headlines is also a matter of speculation, but I rest my case.

I certainly cannot assert that a 40 bit key cannot be decyphered. However, I do not think that the RSA unqualified claims offer full and appropriate disclosure.

Paul

At 10:21 AM -0500 1/30/97, Wright Larry wrote:

...

Following provided for your information.

EXPORTABLE CRYPTOGRAPHY TOTALLY INSECURE: CHALLENGE CIPHER BROKEN IMMEDIATELY

January 28, 1997 - Ian Goldberg, a UC Berkeley graduate student, announced today that he had successfully cracked RSA Data Security Inc.'s 40-bit challenge cipher in just under 3.5 hours.

RSA challenged scientists to break their encryption technology, offering a $1000 award for breaking the weakest version of the code. Their offering was designed to stimulate research and practical experience with the security of today's codes.

The number of bits in a cipher is an indication of the maximum level of security the cipher can provide. Each additional bit doubles the potential security level of the cipher. A recent panel of experts recommended using 90-bit ciphers, and 128-bit ciphers are commonly used throughout the world, but US government regulations restrict exportable US products to a mere 40 bits.

Goldberg's announcement, which came just three and a half hours after RSA started their contest, provides very strong evidence that 40-bit ciphers are totally unsuitable for practical security. "This is the final proof of what we've known for years: 40-bit encryption technology is obsolete," Goldberg said.

<...Rest of the nnouncement from UC Berkeley snipped>

Paul A. Strassmann 55 Talmadge Hill Road, New Canaan, CT. 06840 Telephone: 203-966-5505; Fax: 203-966-5506 INTERNET: paul@strassmann.com WorldwideWeb: http://www.strassmann.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~