The lock industry defines a high security lock cylinder as;
The secrets of operation, picking and impressioning pin tumbler cylinders are not really secrets any more. You can find detailed instructions for the above defeat techniques in the FAQ for some newsgroups on the internet. While most pin tumbler cylinders have the capability of at least 100,000 different combinations to as many as 1,000,000, only around 30,000 or so are actually used by most lock manufacturers for the keyed different locks you can buy off the shelf. Since a particular brand of lock is usually very popular in a particular geographic area and the population usually exceeds 30,000...........................
Yes, most likely there are at least two houses that have the same key.
In the late 1960's a new type of cylinder came on the market. It was a cylinder which represented a new design that wasn't susceptible to the same method of attack as the pin tumbler cylinder in use since 1858. Most of these cylinders still used pin tumblers but they also had another secondary locking mechanism which couldn't be picked or impressioned with any ease and they offered millions of different usable combinations. This type of cylinder was able to offer another feature that had been missing since around the beginning of the century, patent protected keys.
Because the keys were part of the new lock design they could be protected regarding duplication capabilities. Blanks were not available except from the original manufacturer and special techniques and sometimes machinery were required to duplicate them.
Manufacturers of these high security cylinders have entered into contractual agreements with certain locksmiths who have duplicating capability and have been certified for service. While those original patents from the 1960's have expired, there are new ones available now. Most of these cylinders are listed as high security devices by the Underwriters Laboratories and offer genuine key control as well as resistance to physical attack.
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