High Security Car Keys Explained
A high security car key is a key whose blade carries a groove milled into its flat face, also called a laser cut or sidewinder key, and whose transponder chip is checked by the immobiliser before the engine starts.
Inta-Lock Car Key Guides. Updated October 2026.
The name describes the blade. A standard car key carries notches along its edge, while a high security key carries a winding track down the middle of the blade, cut by a milling machine and not by a laser. The chip and the blade are separate parts in one shell, and each does a different job.
A replacement is cut and then coded to the car, so the work has two stages. The blade type alone does not stop a theft, and the cost of a new key moves with the key type, the vehicle and whether a working key still exists.
What Is a High Security Car Key?
A high security car key is a car key with a milled blade, where the cuts run as a groove along the flat face of the blade instead of as notches along its edge.
Three names describe the same blade. High security key, laser cut key and sidewinder key all refer to the winding track that runs down the centre of the blade. The track is the part the lock reads.
The term is a trade name for the blade type. On a modern car the same key also holds a transponder chip, and many hold a remote as well, so the phrase high security car key is used for the whole key and not only for its metal.
The security of the car rests on three things working together, which are the door and ignition locks, the chip inside the key and the immobiliser inside the car.
How Do You Tell if a Car Key Is High Security?
A high security car key shows a wavy groove milled along the flat face of the blade, where a standard key shows a row of notches cut into its edge.
- The face of the blade. The face of the blade carries the cuts. Hold the key flat and a winding channel runs along the middle, often on both faces.
- The edges of the blade. The edges of a high security blade are straight and smooth on most designs. A standard blade has a saw tooth edge on one side or on both.
- The thickness of the blade. The blade of a high security key is a thick, rectangular bar. A standard blade is thinner and tapers towards the notches.
- A blade hidden in the fob. A flip key folds its blade into the fob, and a keyless key hides a small emergency blade inside its case. Both blades are usually milled in the same way.
Where the blade is hard to read, the key type of the car is confirmed on the call from the registration.
What Does Each Part of a High Security Key Do?
Each part of a high security key does one job, with the blade turning the lock, the chip answering the immobiliser, the remote working the central locking and the emergency blade opening the door when the electronics fail.
| Part of the key | What the part does | What happens when it does not match the car | How a new one is made |
|---|---|---|---|
| The milled blade | Turns the door lock and, on a car with a key ignition, the ignition lock | The blade does not turn, or does not enter the lock at all | Milled on a key cutting machine to the cuts the lock takes |
| The transponder chip | Answers the immobiliser of the car when the key is used to start it | The blade turns and the engine does not start | Programmed to the immobiliser with diagnostic equipment |
| The remote | Locks and unlocks the doors from the buttons on the fob | The buttons do nothing, while the blade and the chip still work | Programmed to the car as a separate step from the chip on many cars |
| The emergency blade of a keyless key | Opens the driver door when the fob battery or the car battery is flat | The door stays shut on the day the remote fails | Milled to the door lock, as for any other high security blade |
The table is the reason a key cut from a photograph or bought as a blank does not start a car on its own. The blade is one part of four.
A high security key for a car in Leicester or Leicestershire is cut and coded at the vehicle by Matt.
Call Matt on 0116 442 2084How Does It Differ From a Standard Car Key?
A high security key differs from a standard car key in where the cuts sit and in the machine that makes them, while the chip inside works in the same way on both.
- Notches are cut into one edge or both edges of the blade.
- The blade is cut on an edge cutting machine.
- The lock reads the height of each notch.
- A transponder chip sits in the head of the key on a car with an immobiliser.
- A groove is milled into the flat face of the blade.
- The blade is cut on a milling machine that follows the cuts of the lock.
- The lock reads the path of the groove.
- A transponder chip sits in the head or the fob of the key in the same way.
Both key types start the car only when the chip is accepted, so a milled blade is not what separates a key that starts the engine from one that does not.
How Is a High Security Key Cut and Programmed?
Six steps take a high security key from a phone call to a key that turns the lock, starts the engine and works the remote.
- Call Matt on 0116 442 2084 with the make, the model, the year and the registration of the car, and say whether a working key still exists.
- A quote is agreed before work begins. Matt is with you within the hour in Leicester, and the same day across Leicestershire.
- Identity and authority to request the work are checked before key work starts. The V5C vehicle registration certificate, which names the registered keeper, and photo identification are common examples, and what applies is confirmed on the call.
- The blade is milled at the vehicle to the cuts the lock of the car takes. A working key gives those cuts where one exists, and what applies on a car with no key left is confirmed on the call.
- The transponder chip and the remote are coded to the car. That stage is the car key programming in Leicester service, where a key, a remote or a proximity fob is matched to the immobiliser.
- A finished high security key turns the door lock and the ignition, starts the engine and works each remote button.
A blade that is cut and not coded opens the door and leaves the engine off, which is why a replacement key takes both stages.
Does a High Security Key Stop Car Theft?
No, a high security key does not stop car theft on its own, because the milled blade protects the lock while the immobiliser, the alarm and the way the key is stored protect the rest of the car.
The name belongs to the blade and not to a certificate. Thatcham Research certification applies to alarm, immobiliser and tracking systems, and its advice on how to increase car security names the relay attack as a theft method aimed at cars with passive keyless entry and start. A relay attack works on the radio signal of the fob, so the blade of the key plays no part in it.
The same advice is to store keys, spares included, in a signal blocking pouch, and to check in the handbook whether the keyless fob switches off at night.
What Moves the Cost of a High Security Key?
The cost of a high security key moves with the key type, the vehicle, whether a working key exists and where the car stands, and a quote is agreed before work begins.
- The key type. A blade with a chip sits at the lower end. A remote key costs more, and a keyless key with its emergency blade costs more again, because each adds a part that is supplied and coded.
- The vehicle. The make, the model and the year decide the blade profile and the immobiliser system. A system that takes more stages to code raises the cost.
- A working key or none. A spare made while one key still works costs less than a key made after every key is lost, because a lost key job starts with entry to the car and the lock.
- Where the car stands. The work takes place at the vehicle, and the figure is confirmed from the registration and the location on the call.
No price list is published. The key type, the chip and the figure for the car are confirmed on the call.
Which Related Questions Follow a High Security Key?
Four situations sit beside the plain question of what a high security key is, and each one belongs to a different page or a different job.
How Does Cutting a Key Differ From Programming It?
Cutting shapes the metal of the key to the lock, while programming matches the chip of the key to the immobiliser. A high security key takes both, and neither stage replaces the other.
The cutting stage, with the blade profiles and the machines used for an edge cut blade and a milled blade, is the work of the car key cutting service.
What If a Key Matches Neither Blade Type?
Some keys carry no visible blade, and some carry a blade with dimples or with cuts on four sides. The blade is one of several ways to sort a car key, and the full set, from a plain blade to a keyless fob, is laid out for anyone working out which car key your vehicle carries.
Is a Keyless Key Open to a Relay Attack?
A keyless key holds a high security emergency blade and a radio circuit, and the theft risk sits with the circuit. The ways a relay attack is blocked, at home and at the car, are set out under keyless car theft prevention.
What About a Used Car With One Key?
A used car that arrives with one key leaves a second key unaccounted for. Thatcham Research advice for a car bought second hand with only one working key is to have the missing keys deleted and a spare added as soon as possible.
Where a key is missing, missing electronic keys are removed from the immobiliser memory where the vehicle supports it. A mechanical blade still turns a physical lock unless that lock is changed or rekeyed. A second key made while the first still works is the job of the spare car keys service.
Call Matt with the registration of the car, and the blade, the chip and the quote for a high security key are confirmed on the call.
Frequently Asked Questions
Is a laser cut key the same as a high security key?
Yes, a laser cut key and a high security key are the same thing, a car key with a groove milled into the flat face of the blade.
Sidewinder key is a third name for the same blade.
Is a laser cut key cut with a laser?
No, a laser cut key is cut by a milling cutter on a key cutting machine, and the name refers to the precision of the cut.
The cutter follows the track that the lock of the car takes, and no laser touches the blade.
Does a high security key have a transponder chip?
Yes, a high security key for a car with an immobiliser holds a transponder chip, and the chip is a separate part from the milled blade.
The blade turns the lock and the chip lets the engine start, so a new key is both cut and programmed.
Which cars use high security keys?
The blade type of a car depends on its make, its model and its year, and no single list covers it.
The quickest check is the key itself. A groove on the flat face of the blade is a high security key, and the key type of the car is confirmed on the call.
Is a spare made from a working high security key?
Yes, a spare high security key is cut and programmed from a working key on supported vehicles.
The working key gives the cuts of the blade, and the new chip is then coded to the immobiliser of the car.
Is a high security key replaced when every key is lost?
Yes, a high security key is made with no key present on supported vehicles, with the blade cut to the lock of the car and the chip programmed to the immobiliser.
Identity and authority to request the work are checked first, and what applies is confirmed on the call.
How much does a high security car key cost?
The cost of a high security car key is quoted for the individual car, and a quote is agreed before work begins.
The key type, the vehicle and whether a working key exists all move the figure. No price list is published.