Lesson 6: Master Key Systems - Part 2What is a Master Key?
A master key is any key that opens many locks, where each lock has its own individual key. For example, each rental unit in the apartment building has its own unique lock and key, but the landlord has a key that can open all of the rental units. A master key system is when you apply the master key algorithm to rekey a series of locks to operate with a master key.
Master pins are smaller than top pins. Each key cut is coded according to its depth; likewise, each matching pin receives the same code. When the key enters the cylinder the depths align with the pins in the cylinder to form a sheer line. Master pins stack between the top and bottom pins and allow for multiple sheer lines. This means that multiple different keys can engage the cylinder.
Master key systems can be as small as 2 locks in a system, but as expansive as hundreds or even thousands of locks. Large master key systems often rely on hierarchies of master keys. I will use the example of a college to exemplify how this hierarchy works. Each teacher has a key to their classroom. This key is called the proper key. Every department head would have a sub master or group master key which would be able to open all the doors in that department. Thus an English teacher would only be able to unlock their classroom door. The head of the English department could open every door in the English department, but none of the doors in the other departments. The grandmaster key could open all doors in the entire college. This would be given to the janitorial staff, building super, and college dean. Master key systems are expansive enough to incorporate all kinds of specificity. This is a convenient and effecients means of governing access control.