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Looking for rolling codes algorithm

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PaulHolland

PaulHolland

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Hi All,

I am looking for a rolling code algorithm also known as a hopping code who knows a good algorithm that can be implemented in hardware + software....

regards,

Paul.
 

We didn't understand, would you like to repeat again ?? :wink:

It's pretty useless reiterate same message four times. If someone here have it and want help he will reply, don't worry.
 

please clarify your question.

are you looking for the algorithm as used in a car key fob (keyless entry)
or garage door opener? this is just simple PRBS and can be implemented
as a shift register with XOR taps, pretty easy.
 

The algorithm will not be used for car key's or something like this...

OK how does the receiver sync with the transmitter of the running code ??..

can you give an example..

regards,

Paul Holland
 

there are several open source implementation based on linux ... look for one time password or similar solution as far as i understood your qeustion ...
 

PaulHolland said:
OK how does the receiver sync with the transmitter of the running code ??
Click to expand...

you need to reset the transmitter and receiver before putting them in use.
then, whenever the transmitter sends a code and the receiver gets it,
the code changes to the next one, it's that easy. transmitter and receiver
are running the same algorithm and a comparison is done at the receiver.
the only trick is you need to allow a code range at the receiver in case
that the transmitter sends a signal while the receiver does not get it.
most car keyfobs allow a 256 forward search range. (it's not a problem to
do this in a keyless entry or garage door opener situation, but it will be
if you are using this algorithm in a high-speed application)
 

Re: rolling code algorithm

suggest use microchip HCS200 serial
you can google HCS200 will find the reciver and transmiter
this is ver easy use hopping code IC
 

I am looking for any possible vulnerabilities in Microchip HCS200 KEELOQ® Code Hopping Encoder. More specifically I am analyzing this security protocol to find flaws in it. Could any of you help me out? Thanks!
 

HCS200 KEELOQ has been broken already some years ago. Microchip has introduced a new chip with a better code this time :). HCS200 is being used in about 80% of the remote car fobs and lots and lots of cars are now stolen and broken into.
 

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