Entries Tagged "cryptography"

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More on the Unabomber's Code

Last month I posted about Ted Kaczynski’s pencil-and-paper cryptography. It seems that he invented his own cipher, which the police couldn’t crack until they found a description of the code amongst his personal papers.

The link I found was from KPIX, a CBS affiliate in the San Francisco area. Some time after writing it, I was contacted by the station and asked to comment on some other pieces of the Unabomber’s cryptography for a future story (video online).

There were five new pages of Unabomber evidence that I talked about (1, 2, 3, 4, and 5). All five pages were presented to me as being pages written by the Unabomber, but it seems pretty obvious to me that pages 4 and 5, rather than being Kaczynski’s own key, are notes written by a cryptanalyst trying to break the Unabomber’s code.

In any case, it’s all fascinating.

Posted on January 3, 2007 at 6:59 AM • View Comments

AACS Cracked?

This is a big deal. AACS (Advanced Access Content System), the copy protection is used in both Blu Ray and HD DVD, might have been cracked—but it’s still a rumor.

If it’s true, what will be interesting is the system’s in-the-field recovery system. Will it work?

Hypothetical fallout could be something like this: if PowerDVD is the source of the keys, an AACS initiative will be launched to revoke the player’s keys to render it inoperable and in need of an update. There is some confusion regarding this process, however. It is not the case that you can protect a cracked player by hiding it offline (the idea being that the player will never “update” with new code that way). Instead, the player’s existing keys will be revoked at the disc level, meaning that new pressings of discs won’t play on the cracked player. In this way, hiding a player from updates will not result in having a cracked player that will work throughout the years. It could mean that all bets are off for discs that are currently playable on the cracked player, however (provided it is not updated). Again, this is all hypothetical at this time.

Copy protection is inherently futile. The best it can be is a neverending arms race, which is why Big Media is increasingly relying on legal and social barriers.

EDITED TO ADD (12/30): An update.

EDITED TO ADD (1/3): More info from the author of the tool.

EDITED TO ADD (1/12): Excellent multi-part analysis here.

EDITED TO ADD (1/16): Part five of the above series of essays. And keys for different movies are starting to appear.

Posted on December 29, 2006 at 6:02 AM • View Comments

Class Break of TiVoToGo DRM

Last week I wrote about the security problems of having a secret stored in a device given to your attacker, and how they are vulnerable to class breaks. I singled out DRM systems as being particularly vulnerable to this kind of security problem.

This week we have an example: The DRM in TiVoToGo has been cracked:

An open source command-line utility that converts TiVoToGo movies into an MPEG file and strips the DRM is now available online. Released under a BSD license, the utility—called TiVo File Decoder—builds on the extensive reverse engineering efforts of the TiVo hacking community. The goal of the project is to bring TiVo media viewing capabilities to unsupported platforms like OS X and the open source Linux operating system. TiVoToGo support is currently only available on Windows.

EDITED TO ADD (12/8): I have been told that TiVoTo Go has not been hacked: “The decryption engine has been reverse engineered in cross-platform code – replicating what TiVo already provides customers on the Windows platform (in the form of TiVo Desktop software). Each customer’s unique Media Access Key (MAK) is still needed as a *key* to decrypt content from their particular TiVo unit. I can’t decrypt shows from your TiVo, and you can’t decrypt shows from mine. Until someone figures out how to produce or bypass the required MAK, it hasn’t been cracked.”

And here’s a guide to installing TiVoToGo on your Mac.

EDITED TO ADD (12/17): Log of several hackers working on the problem. Interesting.

Posted on December 7, 2006 at 12:42 PM • View Comments

The Unabomber's Code

This is interesting. Ted Kaczynski wrote in code:

In a small journal written in code, he documented his thoughts about the crimes he was committing. That code was so difficult, a source says the CIA couldn’t crack it—until someone found the key itself among other documents, and then translated it.

Look at the photo. It was a manual, pencil-and-paper cipher. Does anyone know the details of the algorithm?

Posted on December 6, 2006 at 12:53 PM • View Comments

David Kahn Donates his Cryptology Library

According to The New York Times:

The National Cryptologic Museum, at Fort Meade, Md., home of thousands of code-breaking and code-making artifacts dating back to the 1500s, has acquired a major collection of books on codes and ciphers, the museum said. It was donated by David Kahn, a leading American scholar of cryptology and the author of “The Codebreakers: The Story of Secret Writing.” The collection includes “Polygraphiae Libri Sex” (1518) by Johannes Trithemius, the first known printed book on cryptology, along with notes of interviews with modern cryptologists, memos, photocopies and pamphlets. About a dozen items from the collection are currently on display.

Posted on November 24, 2006 at 7:55 AM • View Comments

New Timing Attack Against RSA

A new paper describes a timing attack against RSA, one that bypasses existing security measures against these sorts of attacks. The attack described is optimized for the Pentium 4, and is particularly suited for applications like DRM.

Meta moral: If Alice controls the device, and Bob wants to control secrets inside the device, Bob has a very difficult security problem. These “side-channel” attacks—timing, power, radiation, etc.—allow Alice to mount some very devastating attacks against Bob’s secrets.

I’m going to write more about this for Wired next week, but for now you can read the paper, the Slashdot thread, and the essay I wrote in 1998 about side-channel attacks (also this academic paper).

Posted on November 21, 2006 at 7:24 AM • View Comments

Classical Crypto with Lasers

I simply don’t have the physics background to evaluate this:

Scheuer and Yariv’s concept for key distribution involves establishing a laser oscillation between the two users, who each decide how to reflect the light at their end by choosing one of three mirrors that peak at different frequencies.

Before a key is exchanged, the users reset the system by using the first mirror. Then they both randomly select a bit (either 1 or 0) and choose the corresponding mirror out of the other two, causing the lasing properties (wavelength and intensity) to shift in accordance with the mirror they chose. Because each user knows his or her own bit, they can determine the value of each other’s bits; but an eavesdropper, who doesn’t know either bit, could only figure out the correlation between bits, but not the bits themselves. Similar to quantum key distribution systems, the bit exchange is successful in about 50% of the cases.

“For a nice analogy, consider a very large ‘justice scale’ where Alice is at one side and Bob is at the other,” said Scheuer. “Both Alice and Bob have a set of two weights (say one pound representing ‘0’ and two pounds representing ‘1’). To exchange a bit, Alice and Bob randomly select a bit and put the corresponding weight on the scales. If they pick different bits, the scales will tilt toward the heavy weight, thus indicating who picked ‘1’ and who picked ‘0.’ If however, they choose the same bit, the scales will remain balanced, regardless whether they (both) picked ‘0’ or ‘1.’ These bits can be used for the key because Eve, who in this analogy can only observe the tilt of the scales, cannot deduce the exchanged bit (in the previous case, Eve could deduce the bits). Of course, there are some differences between the laser concept and the scales analogy: in the laser system, the successful bit exchanges occur when Alice and Bob pick opposite bits, and not identical; also, there is the third state needed for resetting the laser, etc. But the underlying concept is the same: the system uses some symmetry properties to ‘calculate’ the correlation between the bits selected in each side, and it reveals only the correlation. For Alice and Bob, this is enough—but not for Eve.”

But this quote gives me pause:

Although users can’t easily detect an eavesdropper here, the system increases the difficulty of eavesdropping “almost arbitrarily,” making detecting eavesdroppers almost unnecessary.

EDITED TO ADD (11/6): Here’s the paper.

Posted on November 6, 2006 at 7:49 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.