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Medeco Readies Assembly-Line Fix for DefCon Lock Hack
From: InfoSec News <alerts () infosecnews org>
Date: Fri, 10 Aug 2007 01:33:19 -0500 (CDT)

http://www.wired.com/politics/security/news/2007/08/medeco

By Kim Zetter
Wired.com
08.09.07

High-security lock manufacturer Medeco says it's planning a design 
change to counter one of two attacks against its products that were 
described at the DefCon hacking conference over the weekend, boosting 
security on a line of locks found at the White House, the Pentagon, 
embassies and other critical locations.

On Sunday, three researchers led by lock-picking expert Marc Webber 
Tobias showed how they could easily "bump" and pick Biaxial and 
high-security M3 locks made by Medeco Security Locks, a Virginia-based 
company that claimed last year that its locks were "bump-proof."

The only tools the researchers needed to bump the Biaxial lock was a 
special bump key and a hammer. The M3 lock, which comes with an added 
slider feature, required an additional tool -- a paper clip.

Matt Blaze, a professor of computer and information science at the 
University of Pennsylvania who has written about master-key locks, says 
the researchers' work is impressive and concerning.

"Medeco locks are marketed to people who want to use them for 
high-security applications," Blaze says. "They're widely trusted to be 
very, very secure and are regarded as effectively pick-proof in 
practice. So any time there is an attack against this kind of lock, 
particularly a non-destructive kind of attack (that doesn't show 
evidence of an attack), that's very surprising."

Privately, the researchers also showed Wired News a new type of attack 
on deadbolt locks that requires only a modified $2 screwdriver and a 
wire shim device. Wired News agreed not to publish the details of the 
technique, but the researchers say it exploits a flaw present in 
single-cylinder deadbolts -- those that have a single-sided key entry 
with a flip switch on other side. It does not work on deadbolts that 
require a key on both sides of the lock.

The researchers demonstrated this technique on Medeco's M3, though they 
say it will work on all brands of single-cylinder deadbolts.

"The interface for deadbolts is defective," says Tobias, an 
investigative lawyer and author. "I don't want to create a panic, but 
this needs to get fixed."

Clyde Roberson, director of technical services at Medeco, acknowledged 
that the researchers might be right about the deadbolt problem. This 
week the company rapidly developed what he hopes is a hardware solution 
to the vulnerability, and Roberson is scheduled to fly to Florida on 
Thursday to meet privately with one of Tobias' researchers to see their 
attack on the lock and try out the fix.

Medeco hopes to roll out the solution on its factory floor this Friday 
if tests show the solution works.

But Roberson is more skeptical about the bumping demonstration. He told 
Wired News he thinks the researchers' claims are untrue and Medeco locks 
are still bump proof.

"We stand behind our locks," Roberson said. "We don't believe you can 
use a bump key on Biaxial or M3 (locks) at all, whether it's with a 
paper clip or not. We believe that this information is factually 
incorrect."

Bumping uses kinetic energy to open a lock with a specially cut key. The 
attacker inserts a bump key into a lock, and then raps it with a small 
hammer. The energy created by the impact travels through the key and 
causes the locking pins inside the lock cylinder to separate, allowing 
the cylinder to turn and unlock the device.

The attack is considered a serious threat because, like lock-picking, 
it's a covert technique for breaking into a locked door that leaves no 
obvious telltale evidence behind (though forensic examiners who 
scrutinize the inside of the lock might find little marks on the 
internal pins).

Although locksmiths and covert-entry specialists have known about and 
practiced bumping for years, the general public became aware of it only 
in the last two years after researchers disclosed the industry secret, 
and videos showing how to bump locks appeared on the internet.

It's been widely believed that Medeco's high-security locks were 
impervious to the technique. In a conventional pin-tumbler lock, each 
cut in the user's key lifts the corresponding pin in the lock to the 
exact height needed to turn the cylinder. But Medeco's patented pin 
tumbler locks also require the key to rotate the pin to one of three 
orientations -- left, right or center. The feature has made its Biaxial 
high-security locks a favorite for years with customers who sought extra 
protection.

When bumping received national media attention last year, the company 
even issued a press release boasting that its locks are "bump proof."

Tobias and his colleagues began testing that claim a year ago last April 
through a combination of computational analysis and mechanical tests. 
Using computers, they analyzed and crunched Medeco's published 
non-master-key codes to determine how many bump keys they would need to 
make to encompass all of the possible key-code combinations. (Lock 
companies publish such codes so that locksmiths can create keys for the 
locks.)

Medeco's keys have a special feature in that the bidding on them (the 
peaks and valleys) is cut at different angles and different offsets 
(spacing). These angles and offsets can be combined in more than a 
million variations to create keys that are unique to each lock. Using a 
computer, however, and taking advantage of engineering tolerances in the 
lock, the researchers crunched the codes and synthesized the 
combinations to create fewer than a dozen keys (they've asked us not to 
disclose the exact number) that will fit into numerous Medeco Biaxial 
and M3 locks.

Blaze says the approach is impressive.

"It's interesting to see how this combination of mechanical and computer 
analytical methods can be used to attack these things," he says. "If 
you're just looking at these things in mechanical terms or you're just 
looking at these things in computational terms, you won't be able to 
attack them successfully. The combination of the two, I think, is fairly 
unique and pretty clever."

Even then, the researcher's technique should have failed against 
Medeco's newest lock, the high-security M3 introduced in 2005. An 
improvement on the old Biaxial, the M3 cylinders feature a slider 
inside. A patented bar on the side of the key has to push in the slider 
in order for the key to enter.

But the researchers, among them computer security researcher Matt 
Fiddler and a professional locksmith who asked not to be named, found a 
way to bypass the slider on the M3 locks as well. They simply use a 
modified paper clip to push back the slider and then bump the lock as if 
it were a previous-generation Biaxial lock.

To demonstrate their bumping technique against Medeco's M3 lock for 
Wired News, Tobias took a lock and inserted one of the keys that he and 
his researchers designed from Medeco's codes, then hit it several times 
with a bump hammer and turned the key.

Tobias says that last year his group provided Medeco with full 
documentation of their techniques as well as video showing them cracking 
the locks. But Medeco's Roberson dismissed their claims after Tobias 
visited him last October to show him the technique. Although Tobias was 
able to open locks he'd brought with him, he was unable to bump open 
locks that Roberson pulled directly from the factory line. Tobias says 
this is because his team was still perfecting the bump keys at the time, 
and that he was able to open those same locks later after the design of 
the bump keys was tweaked and the keys were re-cut.

The failed demonstration is what left Medeco's Roberson initially 
unconvinced of Tobias's claims. Roberson adds that since then Medeco 
researchers have not been able to replicate the bumping claims, he 
thinks the researchers simply designed one bump key to open one lock 
used in their demonstration, which wouldnt open other locks.

"A bump key is something that works on any cylinder that you walk up 
to," Roberson says. "They couldnt walk up to a random lock on a door and 
open it."

Tobias says that contrary to Roberson's statement, their bump key has 
worked on more than one lock.

"We've opened many, many locks with the bump keys," he says. 
"Theoretically, we can open all of the M3 locks, but we don't know for 
sure. What if we can open just 50 percent of them? The question is ... 
what percentage becomes a threat?"

Tobias has posted a security alert about the M3 deadbolts to a 
restricted industry site for professional locksmiths and next month 
he'll meet with representatives of the Underwriters Laboratories -- the 
lab that tests and creates standards for manufacturers' products -- to 
discuss improving the standard for such locks. Currently the standards 
don't test for bumping.

Two other companies that manufacture deadbolt locks -- Schlage and Abloy 
-- did not respond to calls by press time.

Blaze says that Tobias' claims shouldnt be dismissed.

"We can all be excused for not having realized this was possible before 
somebody pointed it out to us, but I think the big question is, now that 
somebody has figured it out, how is Medeco going to react? Hopefully 
Medeco will acknowledge the problem and look for ways to correct it," he 
says.

Roberson will be discussing the bumping attacks again during his 
Thursday meeting with Tobias' research partner, and says Medeco is 
conducting additional tests of the bumping attack with independent 
testers. He says if he's satisfied that the researchers' claims are 
true, the company will address the issue.

"There's always a possibility that we're wrong," he says.


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