From previous guys video description, using the resistance feedback technique and grouping wheels.
This lock takes about 10 minutes on average to open with no special skills. This type of issue is common with many laptop locks. It would be nice to have a rating for these types of locks as do safes.
Kensington Product Number: K64588US
UPC: 085896645887The basic method consists of testing the resistance of two wheels simultaneously for 100 combinations of the remaining two wheels. All the while, testing for resistance as indicators of correct combinations.
The working:
In the following process the topmost wheel is wheel A, the nextmost is B, then C, and D.Wheels A and D are cycled through the following 100 combinations.
A = 0, D = 0
A = 1, D = 0
a = 2, D = 0
...
A = 7, D = 9
A = 8, D = 9
A = 9, D = 9After setting each of the 100 combinations the button is depressed slightly and the two central wheels, B and C are tested for resistance. This mechanical feedback tells the manipulator which of the test combinations creates additional pressure on the central B and C wheels as the A and D wheels approach their correct positions. This additional pressure is created as the fence travels further down the center of the lock and has more of an effect on the central wheels.
This is continued for all 100 possible combinations of A and D. There will be one combination of A and D where B and C are locked in place and cannot be rotated. The values for A and D are now determined. There are now 100 remaining combinations of wheels B and C.
Repeat the process for B and C as performed previously with wheels A and D. In a perfect manipulation this process requires 200 test combinations. Therefore, out of the 10,000 possible combinations 200 are required to be tested to open the lock in a perfect manipulation. This means, the actual keyspace is 2% of the lock's possible combinations.
The effective keyspace can be reduced further by determining which of the wheels B or C can provide the most information via mechanical feedback. This can be done by pressing slightly on the button and determining which central wheel has moves the most easily. Turn that wheel until it encounters some resistance. Then perform the same technique with the other wheel. This reduces the total tests to 100 + a spin of a central wheel [10] + a spin of the other central wheel [10] = 120 test combinations.
*The process below the wheels could be lettered in any manner. In this particular lock it is easiest to cycle through the first 100 combinations on the A and D wheels and test and B & C. If the wheels to test are not adjacent they cannot be rotated together and the test would, therefore, require testing each wheel separately.