Knock lock

[Dartan]

http://www.isracast.com/Articles/Article.aspx?ID=158

This sure is interesting...has anybody else heard of this before?

Dave

[Omikron]

Grr....I was JUST about to post about that!

Anyway, yes I HAVE heard of this type of techonology before and E-Lock are *NOT* the first ones to do it. They are however, the first ones to try and produce a commercial product based on the technology.

Initially, I was worried that someone would be able to record the knock sequence and play it back. However, the article claims that the knock sequence changes every time. This would mean that the both the lock and the key are using the same rolling algorithm to generate knocks. This presents two problems.

First, if the algorithm were ever discovered, then anyone could find the next knock code in the sequence by just using a combination of the recorded knock and the algorithm. Second, if the knock sequence changes, how are other keys notified of this change? How has the system been designed for use with different keys?

What is the longevity and durability of the lock? After all, the both the lock AND the key have moving parts! What if you break your key? How much do replacement keys cost?

Furthermore, when you reprogram the lock, how long does THAT take? What is the process of adding athorized knock keys and deactivating old ones? It really seems that this knocking system is more of a noveltey than anything else. RFID based systems use far less power and have much more flexibility in their design.

I give it two thumbs down.

[Dartan]

I think the algorithm works the same way remote entry on cars work. Both the car and the key fob have the next 256 keys (in order) that can open the car. Anyone of those 256 keys can open the car and they do this in case you hit the button while not by the car of if the car doesn't get the signal. But after you hit the button and the car opens they both sync up and you get 256 new trys again.

At least that's my understanding on how cars work (correct me if I'm wrong) and I assume this lock works on the same principle.

But you're right, it sure is complicated and replacement keys can't be cheap or readily available.

Dave

[zeke79]

So if I press the unlock button on my key fob 257 times and then try to unlock my car it will not work! I gotta try this How about a second fob, how does it keep track of the codes if it is rarely used?

[jordyh]

So if I press the unlock button on my key fob 257 times and then try to unlock my car it will not work! I gotta try this

If the car sends a signal back to the "remote controll key" , it could function as a "approval"-sign so that the key knows that it should use the next code the next time.
But if the "approval" was not given by the car (and the car won't open because it is out of range or something like that), the code will not change, and will keep matching the cars code for entry.

That would be my (uneducated) guess of how such things could get avoided (and perhaps how it is avoided, i don't know).

[illusion]

Ahh.. man...

mbell explained this well, but since I can't fully remember it'll have to be a paraphrase...

Code: Select all

A messenger walks up to the castle and speaks the password to the guard standing at the top, the guard marks this password off, and the next day the meesenger uses the next password the guard has on his list.

If somebody listened for the code, and simply came back the next day and repeated it, the guard would know it was an old password, and the impersonator would be shot to death.

Well it went something allong those lines, but I liked it.

[Dartan]

So if I press the unlock button on my key fob 257 times and then try to unlock my car it will not work! I gotta try this How about a second fob, how does it keep track of the codes if it is rarely used?

From what I've heard, you're right, you'd be locked out of your car. Someone I used to work with said their son did that once. He got ahold of it and kept hitting the buttons and when it wouldn't open the car he took it to the dealer and that's the story they told him.

Dave

[Dartan]

So if I press the unlock button on my key fob 257 times and then try to unlock my car it will not work! I gotta try this How about a second fob, how does it keep track of the codes if it is rarely used?

Oh, and for a second fob, it has it's only set of unique ids that are kept track of.

Dave

[Chrispy]

So instead of carrying a small piece of metal, I now have to carry a big bulky "KnocKey" because it's more convenient?