Re: remote entry -key fob programming

"MoPar Man" <MoPar@[EMAIL PROTECTED]
> wrote in message
news:4789AA15.A54FE2BB@[EMAIL PROTECTED]
> maxpower wrote:
>
> > The RKE system and transmitter use a rolling code method  ...
> > The transmitter sends a randomly selected sequence code each time
> > The code increments vary depending on a unique algorithm that
> > is preprogrammed to each transmitter at the time it was built.
> > The sequence changes each time the transmitter is used.
>
> > the sequence code cannot be calculated from the encoded
> > transmission. The receiver module also learns the transmitter
> > id code
>
> So far, what you're saying is that the FOB sends out a different
> sequence each time it's pressed, and that the ID code of the fob can
> be uniquely calculated from the transmitted data stream based on an
> algorythm.
>
> I doubt that the fob actually does generate a completely different
> stream each and every time it's pressed, as I doubt that the designers
> would ever anticipate someone with enough electronic gear would be
> close enough to the car to (a) want to open/unlock the car without
> possessing the real fob or key, (b) be close enough to evesdrop and
> capture the transmission, and (c) possess the electronics required to
> replicate the transmission.  Just consider a use-case situation.
>
> But even if the fob does generate a different stream each time it's
> pressed, then I guess the receiver in the car would have to never
> respond to the same stream twice.
>
> > and initial sequence code at the time of transmitter programming.
> > The receiver then expects the next transmitted sequence code to
> > increment within a predetermined range of numbers
>
> Now that has got to be total bull****.
>
> I can see plenty of situations where the fob and receiver can get out
> of sync with each other.  There would be no need for this
> syncronization if the fob simply generates different streams that
> algorythmically always reduces to the same unique ID code.

http://auto.howstuffworks.com/remote-entry2.htm
>
> > Transmitters and receivers are unique to each vehicle line and
> > will not work.
>
> I guess we'll have to wait and see if John Keith posts back his
> results.
>
> > 1999 Plymouth Voyager and 2000 Dodge Caravan
>
> And by the way, do those 2 vehicles have sentry-key?
>
> If so, would they/could they have the same physical ignition key?