Dudley Lock Serial Number Database
Master locks, ACE Hardware locks, American and Dudley combination locks. After the first number has been located this way, the lock should open in 17 tries. This method will produce a combination for a right-left-right dialing sequence,. Mar 24, 2007 Just added another notch to my belt: my friend's Dudley lock: (new logo/square shackle) black dial/black lettering (B), top rivet hole off-center (filled in), no serial number. I decided to time myself this time: I clocked in 7 minutes, no rush.
Forgot your Master lock combo? Or want some incentive to not use a Master padlock? There’s a website for that.
The video above from Samy Kamar shows how you can crack any Master combination lock within eight tries. It’s a bit long, but here’s Ars Technica’s explanation if you don’t want to sit through the video:
The exploit involves lifting up a locked shackle with one hand while turning the combination dial counterclockwise starting at the number 0 with the other. Before the dial reaches 11, there will be three points where the dial will resist being turned anymore. One of them will be ignored as it is exactly between two whole numbers on the dial. The remaining two locations represent locked positions. Next, an attacker again lifts the locked shackle, this time with less force, while turning the dial clockwise. At some point before a full revolution is completed, the dial will resist being turned. (An attacker can still turn through it but will physically feel the resistance.) This location represents the resistance location. The two locked positions and the one resistance position are then recorded on a Web page that streamlines the exploit.
The page responds with the first digit of the combination and two possible digits for the last digit. By testing which of the possible last digits has more “give,” an attacker can quickly figure out which one is correct. By eliminating the false digit from the Web form, the page will automatically populate the eight possible numbers for the second digit of the combination. Now that the attacker knows the first and last digits and knows the second digit is one of eight possible numbers, the hack is a simple matter of trying each possible combination until the correct one opens the lock.
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We’ve previously seen an illustrated guide to cracking a Master lock, but the online tool makes it much easier and in many fewer tries.
Crack a Master Combination Padlock Redux
Two years ago we highlighted how to crack a Master combination padlock for those of you who may…
Read more ReadBreak open any Master Combo Lock in 8 tries or less! YouTube via Ars Technica
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Master Lock Serial Number Database
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There's a vulnerability in Master Lock branded padlocks that allows anyone to learn the combination in eight or fewer tries, a process that requires less than two minutes and a minimal amount of skill to carry out.
The exploit involves lifting up a locked shackle with one hand while turning the combination dial counterclockwise starting at the number 0 with the other. Before the dial reaches 11, there will be three points where the dial will resist being turned anymore. One of them will be ignored as it is exactly between two whole numbers on the dial. The remaining two locations represent locked positions. Next, an attacker again lifts the locked shackle, this time with less force, while turning the dial clockwise. At some point before a full revolution is completed, the dial will resist being turned. (An attacker can still turn through it but will physically feel the resistance.) This location represents the resistance location. The two locked positions and the one resistance position are then recorded on a Web page that streamlines the exploit.
The page responds with the first digit of the combination and two possible digits for the last digit. By testing which of the possible last digits has more 'give,' an attacker can quickly figure out which one is correct. By eliminating the false digit from the Web form, the page will automatically populate the eight possible numbers for the second digit of the combination.
Now that the attacker knows the first and last digits and knows the second digit is one of eight possible numbers, the hack is a simple matter of trying each possible combination until the correct one opens the lock. The following video provides a simple tutorial.
The technique was devised by Samy Kamkar, a serial hacker who has created everything from stealthy keystroke-pilfering USB chargers to DIY stalker apps that mined Google Streetview. In 2005, he unleashed the Samy worm, a cross-site scripting exploit that knocked MySpace out of commission when it added more than one million MySpace friends to Kamkar's account.
Kamkar told Ars his Master Lock exploit started with a well-known vulnerability that allows Master Lock combinations to be cracked in 100 or fewer tries. He then physically broke open a combination lock and noticed the resistance he observed was caused by two lock parts that touched in a way that revealed important clues about the combination. (He likened the Master Lock design to a side channel in cryptographic devices that can be exploited to obtain the secret key.) Kamkar then made a third observation that was instrumental to his Master Lock exploit: the first and third digit of the combination, when divided by four, always return the same remainder. By combining the insights from all three weaknesses he devised the attack laid out in the video.
It's by no means the only way to break the security of a popular padlock. It comes a few years after Master Lock engineers developed new padlocks that resisted a popular form of attacks using shims made from soft drink cans. Kamkar said he has tried his exploit on more than a dozen Master Lock combination locks, and so far it has worked on all of them. In the coming weeks, he plans to unveil more details, including an Arduino-based robot that streamlines the exploit.
Post updated to change 'any' in the headline to 'many.'
Master Lock Serial Number Lookup
Watch Ars staffers put the hack to the test.