A 2015 Ars Technica report described a technique that security researcher Samy Kamkar said could narrow the combination on some Master Lock dial locks to eight or fewer attempts. The reported approach relied on mechanical feedback and a relationship among combination digits; it was not shown to work on every Master Lock or on current models. This is a historical security report, not a reliable opening guide. If you own a lock and have forgotten its combination, Master Lock provides an official recovery process for some locks with serial numbers.
What the eight-try claim means
On April 28, 2015, Ars Technica reported on a technique devised by Samy Kamkar for cracking many Master Lock combinations. Kamkar described using mechanical feedback from the lock together with a structural relationship among the combination digits to reduce the candidate combinations. The report does not provide grounds to treat the result as universal, and the operational sequence is not reproduced here. Read the Ars Technica report.
Ars said Kamkar had tried the technique on more than a dozen combination locks and that it had worked on those he tried. That is a claim attributed to Kamkar in a 2015 report—not independent verification, a population study, or evidence that a particular lock in use today is affected. “Eight or fewer tries” describes the reported outcome, not a guarantee for an arbitrary lock.
What the report does—and does not—establish
- It describes a limited reported sample. The account concerns locks Kamkar said he had tried; it does not estimate how common the weakness was across all locks.
- It is not a current-model assessment. The report dates to 2015, and the reviewed sources do not establish which current models, if any, are vulnerable or resistant to this particular technique.
- There is no substantiated current prevalence figure. The reported test count cannot be used to infer how many locks are affected today.
Master Lock currently lists combination locks in its product category, but that listing does not say whether any specific model addresses the bypass described in the 2015 report. Do not treat a replacement from the category as confirmed protection without model-specific evidence. See Master Lock’s combination-lock category.
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- Indoor and outdoor lock is best used as a gate lock or shed lock for protection and security from theft; extra long shackle for application flexibility
- Set your own four digit combination lock for easy combination recall; combination change tool included
- Combo lock is constructed with a solid body for strength and weatherability, hardened steel shackle for cut resistance
- 2 in. (51mm) wide lock body; 5/16 in. (8mm) diameter shackle with 2-1/4 in. (57mm) length, 1 in. (25mm) width
- Includes two set your own combination locks
If you have forgotten the combination to your own lock
Master Lock says it may be able to help recover a combination if the lock has a serial number. Its official page describes two routes, both requiring the lock to be unattached. Check the page for current instructions before starting, because service procedures may change. Master Lock: Reset & Retrieve Lost Combinations.
Ask a retailer or distributor
- Take the unattached lock to a Master Lock distributor or retailer.
- Ask the retailer to contact Master Lock about recovering the combination. Master Lock says it does not charge for this retailer service, although the retailer may charge a fee.
Submit a photo through the Contact Us form
- Use Master Lock’s Contact Us form to send an unedited photo that clearly shows the whole unattached lock and its serial number.
- Allow 7–10 days for a response, as stated on the support page accessed October 8, 2026.
Master Lock says it will not provide the combination if the lock is attached to something. Its support page also says a set-your-own combination lock cannot be reset without knowing its current combination and that a new lock may be needed.
Quick Recap
Best Value
- Indoor and outdoor padlock is best used as a school locker lock, gym lock, and gate lock, providing protection and security from theft
- Set your own four-digit combination lock for easy combination recall; Combination change tool included
- Combo lock is constructed with a solid body for strength and weatherability, hardened steel shackle for cut resistance
- 2 inch (51 millimeter) wide lock body; 5/16 inch (8 millimeter) diameter shackle with 1 inch (25 millimeter) length, 1 inch (25 millimeter) width
- Includes two set your own combination locks
Rank #4
- LOCKER LOCK 2-PACK: Master Lock 1500T combination padlocks are ideal for school lockers, gym lockers, employee lockers, cabinets, and indoor storage where keyless security is needed.
- SAME COMBINATION OPENS BOTH: Preset 3-digit combination lock design lets one factory-set code open both padlocks, making it easier to manage multiple lockers without keys.
- BUILT FOR DAILY USE: Metal body with stainless steel cover and hardened steel shackle helps resist cutting and sawing for dependable indoor padlock security.
- ANTI-SHIM PROTECTION: Tamper-resistant combo lock mechanism helps protect against shimming while the dial design provides simple, familiar operation.
- STANDARD LOCKER FIT: 1-7/8 in. wide lock body with 9/32 in. shackle diameter, 3/4 in. shackle length, and 13/16 in. width fits many school and gym locker hasps.
Rank #3
- SECURE MULTIPLE OUTDOOR SPACES: Master Lock M175LFEC2 combination padlock 2-pack helps protect gates, sheds, fences, storage units, and equipment with two heavy duty combo locks.
- RESIST CUTTING & SAWING: Tough-Cut octagonal boron-carbide shackle is 50% harder than hardened steel for dependable heavy duty outdoor padlock security.
- SET YOUR CODE WITH EASE: Resettable 4-digit combination lock lets you create a personalized code without a reset tool; one-directional dial works easily in low light.
- PROTECT AGAINST RAIN & MOISTURE: Hinged dial cover and shackle seal help shield internal parts, making this weatherproof combination lock ideal for gates, sheds, fences, and storage.
- FITS MORE LOCKING APPLICATIONS: Long shackle combination lock has a 2-1/4 in. wide zinc body, reinforced bumper, and 3/8 in. diameter shackle for flexible outdoor use.
Rank #2
- Heavy duty outdoor lock; Maximum security combination lock is best used as a gate lock, shed lock, or storage lock.Note: Measure your door's backset, cross bore and thickness to ensure you find the right fit.Control Method:Application
- Set your own four digit combination lock for easy combination recall; No combination change tool required, Shackle seal and hinged dial cover for superior weather resistance
- Padlock is constructed with a zinc body and reinforced body bumper for strength and reliability; Shackle seal and covered dials for superior weather protection; One directional dial feature for low light applications
- Tough-Cut octagonal boron steel shackle is 50% harder than hardened steel; Roller pin cylinder provides maximum pick and pry resistance
- 2-1/4 inch (57 millimeter) wide lock body; 3/8 inch (10 millimeter) diameter shackle with 1-1/2 inch (38 millimeter) length, 15/16 inch (24 millimeter) width; Extended shackle for application flexibility
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