Aug 04, 2015 Can You Determine the Combination of a Master Lock Using Its Serial Number? Masterlock can provide a lock's combination based on its serial number, but this information is not public record and no customer can determine the combination based on the serial number alone.

Apr 29, 2015 - Or want some incentive to not use a Master padlock? Turning the combination dial counterclockwise starting at the number 0 with the other. Jun 4, 2009 - An easy way to perform a Master Lock combination recovery using. Mike, I have an old Master lock, serial number 900390, and I can't get. Feb 20, 2019 To crack a Master Lock combination lock, download a lost combination form on the Master Lock website. Then, fill out the form and pay to have it notarized. Once you've completed the form, mail it to the Master Lock warehouse along with a photo of the lock and the lock's serial number. Master Lock Combination Recovery - Dreamshire. Blog.dreamshire.com I have a Master Glo lock which is similar to the Sphero and has a serial number on the back that starts with 800.

Find the first sticking point.

As you turn the dial CW with tension on the shackle, you will come to the first clockwise stopping point where you can't turn the dial anymore. Make note of where it stops. Sometimes, the dial will stick right on the numbers, but sometimes the sticking point will be between the numbers. If so, record the number to the half (example: 22.5).^[3]
While continuing to apply tension to the shackle, turn the dial as far left (counter-clockwise) as you can. Make note of the first counter-clockwise (CCW) stopping point. The CCW stopping point and CW stopping point form your sticking 'range', for example, 22.5 to 10. (Note: Some 800XXX and 908xxx locks have a two number sticking range [for example, 28 to 30 and 10 to 12].)^[4]
Determine the first sticking point by finding the number that's in the midpoint of the sticking range. A range of 4 and 5 would have a first sticking point of 4.5. A range of 22.5 and 23.5 would have a first sticking point of 23.
Each set of numbers that you find will have the same range. For example, one group may be 0.25 to 0.75 and another may be 0.5 to 0.25 on either side of the sticking points.

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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.

Master Lock Serial Number Database

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.

Master Lock Serial Number Lookup

Post updated to change 'any' in the headline to 'many.'

Master Lock Serial Number Database Free

Watch Ars staffers put the hack to the test.