Re: Garage Door Protocol

It seems like any sort of one time password protocol is suitable for this
purpose.

OATH-HOTP/TOTP comes to mind. There are also similar protocols utilizing
AES (e.g. Yubikey)


On Tue, Jun 17, 2014 at 9:56 AM, Karp, Alan H <[email protected]> wrote:

> Norm Hardy wrote:
>
> > The "Garage Door Protocol" provides simple protection for commands in a
> > one way channel. http://cap-lore.com/Garage/
>
> If you're allowed to resync every once in a while, you can use S/Key,
> http://en.wikipedia.org/wiki/S/KEY.  (Did you notice the pun in the URL?)
>  The transmitter starts with a secret and a counter c as in all the other
> cases.  The receiver starts with the secret hashed c times.  The
> transmitter hashes the secret c-1 times, transmits the result, and
> decrements the counter.  The receiver hashes the received value.  If it
> matches the stored value, the door opens, and the receiver stores the
> received value.  You handle lost or garbled transmissions by having the
> receiver hash multiple times bounded by the last known value of the
> counter.  Of course, you have to resync with a new secret when c=1.
>
> S/Key is often combined with encryption on the channel, but that's not
> needed here.  A successful MITM attack requires blocking the radio link
> between transmitter and receiver, and even if successful, only allows the
> attacker to open the door on your request.  An attacker gains nothing by
> learning the value stored on the receiver.
>
> ________________________
> Alan Karp
> Principal Scientist
> Enterprise Services, Office of the CTO
> Hewlett-Packard Company
> 1501 Page Mill Road
> Palo Alto, CA 94304
> 1 (650) 386-4568
> http://www.hpl.hp.com/personal/Alan_Karp
>
>
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-- 
Tony Arcieri

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