How IMMOSTOP Keeps Your Car's Digital Key Secure
With IMMOSTOP, your phone is what lets your car start. That makes the link between your phone and the immobiliser the most important thing we build, so the new IMMOSTOP boards and app have security designed in at every step. Here's what protects your car, in plain English.
A unique key for every car
Every IMMOSTOP board makes its own random key. No two cars share one, and there's no master key that opens them all. Your phone holds the key for your car and nobody else's.
A fresh check every time you connect
Each time your phone talks to your car, the board sets it a brand-new random challenge that only your phone can answer. The answer is different every time, so there's nothing useful to record and play back later.
Encrypted pairing
When you first pair your phone, the two devices agree their shared key using a modern key exchange (X25519, the same kind used by secure messaging and banking apps). The key itself is never sent over the air.
Your board locks to you
Once your phone is paired, the board's own button is switched off for good. Nobody can walk up to the car and re-pair it to their phone. Adding a second phone or a tag is done from your phone, in the app.
A recovery code that only works once
If you ever lose every phone, a 14-character recovery code (PUK) gets you back in. It changes after each use, so an old code is worthless, and the board stops accepting attempts after too many wrong ones.
Your password protects every change
Adding a keyring tag, blocking a lost one or registering a new phone all need your own password. Not even an installer can add a key to your car without it.
Lost a tag? Block it remotely
If a keyring tag goes missing, it can be blocked without anyone touching the car. The next time your phone connects, the car stops accepting that tag. A replacement can be made from your board's serial number and posted to you.
Service mode for the garage
Booking a service or MOT? Switch on service mode from your phone and the garage can drive the car without your phone or a tag. Set it to switch itself off after a few starts so you never forget. Turning it off never cuts a running engine.
A locked chip in every board we ship
Every IMMOSTOP board that goes into a customer's car has its memory encrypted and secure boot switched on, and its programming port permanently disabled. The keys inside can't be read off the board, even with it in someone's hands.
Signed updates only
New features and fixes arrive over the air through the app. A board only accepts firmware signed by IMMOSTOP, so nobody else can load their own software onto it.
Keys kept in your phone's secure hardware
The app keeps your car's key inside your phone's hardware-protected key store, the same place banking apps keep theirs, so it can't be copied off the phone.
A tamper-checked app
The IMMOSTOP app checks that it hasn't been modified and that it's running on a genuine phone before it will talk to your car.
Phone-controlled, dual immobilisation with security built in from the board up. See IMMOSTOP, £349 all-in, fitted →