"maxpower" <damnnickname@[EMAIL PROTECTED]
> wrote in message
news:zNmdnYmJIMnPnBfanZ2dnUVZ_t2inZ2d@[EMAIL PROTECTED]
>
> "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****.
>
> Your right it has to be total bull****, But it isnt, google rolling
code!!
> No wait, I will do it for you. http://en.wikipedia.org/wiki/Rolling_code
maxpower, there is nothing in this description that would preclude
the original poster from programming the same keyfob to open multiple
cars - as long as the keyfobs were the same part number AND as
long as the system didn't have a different set of pseudo random number
generators. (PRNGs)
If for example the transmitter had a table of, lets say 200 different
PRNGs, and during keyfob programming the transmitter uploaded
a selected PRNG to the keyfob, then you would have a problem
doing it. What would happen is both vehicles would likely use a
different PRNG.
But, if the PRNG's are only different between vehicle models, and
or years, and the PRNG was burned into the keyfob, then as long
as both cars used the same PRNG you could do it.
I can guarentee to you that at least up to 1995 Chrysler did in fact
use fixed PRNGs in the RKE system. In fact the sequence generator
was the same algorithim for multiple YEARS. That is why I was
able to program both my '94 and '95 van to use the same keyfobs.
They changed the remotes in 96, and I would assume the system
as well. But, if the new keyfobs are transmit-only, then it would be
very likely that keyfobs of the same part number would use the
same PRNG and would work.
Frankly the entire system is way overengineered. A thief simply
walks up to the car and smashes the window with a rock, he does
not bother fiddling around with sniffing RKE signals.
Ted
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