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I'm confused why this is still an unsolved problem. A simple cryptographic challenge with pre-shared keys + button press ought to make key fobs perfectly secure

by mppm 1y ago

I'm confused why this is still an unsolved problem. A simple cryptographic challenge with pre-shared keys + button press ought to make key fobs perfectly secure for all practical purposes. Is there something I'm missing here?

2rsf 1y ago
Battery life maybe? AFAIK most of the remotes works one way only, they don't have a receiver and very low processing power.
PinguTS 1y ago
This adds complexity and with complexity there comes a price tag. That would make the key fob more expansive. It also adds higher power requirements this then comes with new requirements for the battery.
- mppm 1y ago
  Re price tag: you can buy a smartphone for 100$. Surely it is possible to mass produce cheap key fobs with send/receive capability and a tiny crypto module. Re power: Key fobs already do some form of crypto and broadcast. Adding reception capabilities ought not to be that power hungry.
  - Iolaum 1y ago
    Even Better, they can use a smartphone app. We already have a battery-powered device that can emit radio signals in various frequencies!
    - ryandrake 1y ago
      I've got an even better solution: Picture a piece of metal, cut in a specific way as to allow metal "tumblers" inside a small cylinder to turn, engaging and disengaging the locks and/or ignition, whereas other pieces of metal, cut differently, would not allow any motion. I know, it sounds far out there, but we should give it a shot.
      - vel0city 1y ago
        That doesn't sound very secure at all. I've heard there are little known techniques called "lockpicking" and "rakes" that make such technology practically useless.
unnouinceput 1y ago
And how that will protect you from repeater attack? I just steal your car while you are in mall with this just as easy, encryption or not. I don't care about the signal, just that I capture it, send it to my other device near your car and kaboom!, your car unlocked.
- SirMaster 1y ago
  How does repeating work if both the car and key use a code that changes every time, like 2FA app.
  - AlotOfReading 1y ago
    TOTP relies on synchronized clocks, which is far, far too complicated to work here.
- josephcsible 1y ago
  The key fob would always return a response the exact same amount of time after receiving the challenge, so couldn't the car learn the distance by measuring the time of flight?
mberger 1y ago
You have to be able to get new keys made without having an original to read. A database of vin, key would be too big of a target and would have to be shared with dealers anyway so they could program new ones. I'm not a security expert but it seems like it would really shorten battery life on the fob if you wanted to protect against replay attacks by adding a time sensitive value.
- mppm 1y ago
  Key distribution is (as always) an important, but solvable problem. There are some tradeoffs involving centralization vs cost of replacement, but those apply generally, not just in this particular case. As for replay attacks, that's where the button press comes in (like on a hardware security token) -- the key only responds to challenges within a second or so of a button press and the car sets a similar timeout for validity.
GuB-42 1y ago
It requires two-way communication, which makes the system more complex, with all the negatives that come with it. Cars are not very secure by nature: they have easy to break glass windows, and are made of relatively lightweight materials. The key system just needs to match that level of security, and AFAIK, attacks on the keyfob are uncommon compared to other, less subtle techniques. The more complex and sensitive "PKES" system, according to the article already has a challenge-response system, but it doesn't help with relay attacks.
blibble 1y ago
yeah, this is what the article is describing as to what it was like in the early 2000s (assuming no moronic key reuse) the problem is they "improved" the usability it was safe when you had to push a button, but now roles are flipped so the car is the initiator, and doing it constantly the protocol is now subject to a whole entire extra class of attacks it was never designed to deal with

by mppm 1y ago

2rsf 1y ago

Battery life maybe? AFAIK most of the remotes works one way only, they don't have a receiver and very low processing power.

PinguTS 1y ago

This adds complexity and with complexity there comes a price tag. That would make the key fob more expansive. It also adds higher power requirements this then comes with new requirements for the battery.

mppm 1y ago
Re price tag: you can buy a smartphone for 100$. Surely it is possible to mass produce cheap key fobs with send/receive capability and a tiny crypto module. Re power: Key fobs already do some form of crypto and broadcast. Adding reception capabilities ought not to be that power hungry.
- Iolaum 1y ago
  Even Better, they can use a smartphone app. We already have a battery-powered device that can emit radio signals in various frequencies!
  - ryandrake 1y ago
    I've got an even better solution: Picture a piece of metal, cut in a specific way as to allow metal "tumblers" inside a small cylinder to turn, engaging and disengaging the locks and/or ignition, whereas other pieces of metal, cut differently, would not allow any motion. I know, it sounds far out there, but we should give it a shot.
    - vel0city 1y ago
      That doesn't sound very secure at all. I've heard there are little known techniques called "lockpicking" and "rakes" that make such technology practically useless.

unnouinceput 1y ago

And how that will protect you from repeater attack? I just steal your car while you are in mall with this just as easy, encryption or not. I don't care about the signal, just that I capture it, send it to my other device near your car and kaboom!, your car unlocked.

SirMaster 1y ago
How does repeating work if both the car and key use a code that changes every time, like 2FA app.
- AlotOfReading 1y ago
  TOTP relies on synchronized clocks, which is far, far too complicated to work here.
josephcsible 1y ago
The key fob would always return a response the exact same amount of time after receiving the challenge, so couldn't the car learn the distance by measuring the time of flight?

mberger 1y ago

You have to be able to get new keys made without having an original to read. A database of vin, key would be too big of a target and would have to be shared with dealers anyway so they could program new ones. I'm not a security expert but it seems like it would really shorten battery life on the fob if you wanted to protect against replay attacks by adding a time sensitive value.

mppm 1y ago
Key distribution is (as always) an important, but solvable problem. There are some tradeoffs involving centralization vs cost of replacement, but those apply generally, not just in this particular case. As for replay attacks, that's where the button press comes in (like on a hardware security token) -- the key only responds to challenges within a second or so of a button press and the car sets a similar timeout for validity.

GuB-42 1y ago

It requires two-way communication, which makes the system more complex, with all the negatives that come with it. Cars are not very secure by nature: they have easy to break glass windows, and are made of relatively lightweight materials. The key system just needs to match that level of security, and AFAIK, attacks on the keyfob are uncommon compared to other, less subtle techniques. The more complex and sensitive "PKES" system, according to the article already has a challenge-response system, but it doesn't help with relay attacks.

blibble 1y ago

yeah, this is what the article is describing as to what it was like in the early 2000s (assuming no moronic key reuse) the problem is they "improved" the usability it was safe when you had to push a button, but now roles are flipped so the car is the initiator, and doing it constantly the protocol is now subject to a whole entire extra class of attacks it was never designed to deal with