Problems with Master Keys and “Ghost” Keys

Ever feel that someone else has keys to your apartment or condo? Over the years we have received many calls from clients who swear that an unauthorized person has keys to their apartment. Sometimes it is an unfounded fear. For example, many years ago before I became a Vancouver locksmith and Port Coquitlam Locksmith, my home was burglarized and for several years I was overly paranoid about home security.

On the other hand, particularly if you live in an apartment or a multi-unit complex, you may be a victim of a frequent problem that arises with master key systems called “ghost” keys or incidental keys.

Let’s first talk about why someone would want a master key system.

Benefits of Master Key Systems

Many buildings in the Vancouver area are master keyed. Most of our commercial clients prefer to have a master key system of some sort. Even a small business could have a system with:

  • One key for all the entrances and exits
  • One key for all the offices
  • One key for all fire and safety locks and lockouts

Some manufacturers even have nifty master keys that can only turn one way. So they can provide a separate key to employees or contractors to unlock doors in the morning and another to lock the doors at closing. 

Master key systems can include things like floor masters where you can have a key that opens all the locks on the 1st floor but not the 2nd floor, and so on.

For apartment owners and tenants, your concierge or strata council may have a unit master key in case of a fire or flooding incident and you are not home. Also, your mandatory annual fire alarm inspection is a lot easier if someone else can unlock your unit door for that 5 minutes.

Master key systems can also incorporate different keyways from the same manufacturer. Master keys themselves can be subdivided into things called sectional masters to further expand a master key system. 

If this sounds complicated, that’s because it is. These complexities are byproducts of over a hundred years of mechanical key systems that are fundamentally limited by their design which brings us to some of the downsides of master key systems and/or mechanical locks.

Disadvantages of Master Key Systems

As I often tell my clients, there is always a trade-off between convenience and security at any grade of lock hardware. For example, electronic deadbolts are convenient, but for the same price, you can probably buy a fantastic mechanical deadbolt that offers easily 3x the level of security than the electronic deadbolt provides.

When it comes to master key systems, some of the most frequent problems are as follows:

  • Excess wear and tear on lock cylinders – master pins will wear down the lock cylinder faster. They’re like tiny pebbles in your shoes. It might be tolerable at first, but they will eventually cause blisters.
  • Hard to get good key copies – Keys that are part of a master key system should not be copied. They should be cut by code by a locksmith every time. Master keyed cylinders tend to be unforgiving of key copies. Even a 0.0001 of an inch can make a difference.
  • Ghost keys or Incidental keys – Every master key system generates a number of unintentional keys that grow exponentially with the number of cylinders in the system.
Problems with ghost keys

From my point of view as a professional Vancouver locksmith, one of the biggest problems with master key systems are these “ghost” keys. These may sound cool, but they are a plague on key systems that were only resolved with the advent of electronic locks and RFID access cards with hash keys.

Long story short, one 5 pin lock cylinder with one master key and one change (i.e. operating) key, not only has those 2 keys that work in the cylinder but also 30 other key bitting combinations that will also work. 5 pin lock cylinders include all Weiser and Kwikset locks and pretty much all the locks you find at Home Depot and other DIY stores.

If that same cylinder has 6 pins, the problem rises to 62 “ghost”/unintentional/incidental keys.

The more “levels” or the number of master keys you have in a lock cylinder, the worse the problem gets. The more lock cylinders you have using the same master key, the worse the problem gets.

I won’t bore you with the math, but with an exponential growth curve, you can imagine just how quickly this problem can get out of control. This is also the most common reason why your neighbour’s key might work in your lock. If your apartment building is master keyed and has more than 50 units, it’s almost guaranteed that some random key will open someone’s front door.

How to eliminate unauthorized keys

There are a few ways to eliminate unauthorized or unintentional keys. 

  1. Rekey your door and remove it from the building’s master key system. Your strata might not like it, but this will reduce the chance of an unauthorized key opening your lock to 1 in 100,000 for a 5 pin lock cylinder.
  2. If possible, switch an electronic lock. I recommend keyless electronic lock systems. If you opt for a code lock, I recommend a model that uses at least 6 digits if not more. These days, there are even RFID electronic locks for the residential market which are even better but can be a bit pricey for a decent quality one.
  3. If an electronic lock is not possible, how about a high security lock? For all the benefits I have mentioned in other articles, a high security lock cylinder could maintain the same aesthetic look that your strata demands and offer the security you seek.

If you have a business owner or a strata council member with an existing master key system, you should ask yourself when was the last time you performed a master key audit. Do you know where all your master keys are? Do you know how your master key system was designed and if it has any “ghost” keys?

Master key systems can be designed without “ghost” keys. It’s incredibly time and labor intensive. They can be quickly eliminated or identified with the proper software but these key system design software are so expensive and archaic that most non-institutional locksmiths don’t have access to them.

If you are interested in performing a key audit and finding out if your system has “ghost” keys, please call or text me at 6043-363-2760 or email me at It would be my pleasure to help you.

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