[Cryptography] ORWL - The First Open Source, Physically Secure Computer

[Francisco Corella]

> > > Secure Key Fob
> > > 
> > > Each ORWL comes with a key fob that uses the same authentication
> > > technology as smart-cards, with an added ability to detect
> > > proximity. After the initial pairing of the key fob with the ORWL to
> > > generate a shared secret, the key fob’s near field communication (NFC)
> > > is used to authenticate the user, at which point the key fob’s uses
> > > Bluetooth (BLE) to monitor whether or not the user is within
> > > range. Once a user goes out of range, ORWL will lock, requiring the
> > > key fob’s NFC authentication to unlock.
> > 
> > That seems vulnerable to a relay attack.
> 
> Not if they're using latency to determine range; you can't fake the speed of
> light.
> 
> I'm not sure if ORWL is in fact using time-of-flight distance measurement
> instead of the more common received-signal-strength distance measurement, but
> it is possible to do with Bluetooth BLE and some products implement it.

I doubt they are doing any distance measurement at all.  If they did
they would mention it.  When people talk about proximity and refer to
being in or out of range they mean being within signal reach or not.
The distinction between proximity detection and distance measurement
is spelled out in
http://electronicdesign.com/communications/what-s-difference-between-measuring-location-uwb-wi-fi-and-bluetooth <http://electronicdesign.com/communications/what-s-difference-between-measuring-location-uwb-wi-fi-and-bluetooth> :
> First, it’s important to distinguish iBeacons and their role, namely
> proximity detection, from the more general problem of measuring
> location and distance. Proximity sensing is when a device detects that
> it’s within range of another device, such as when a phone enters range
> of a beacon. Detecting proximity doesn’t necessitate measurement of
> distance; rather, it only requires detecting a steady signal. Some of
> these systems distinguish being “in range” of a beacon and being
> “close” to a beacon by distinguishing weak and strong signal
> strengths. However, this still isn’t the same as measuring precise
> distance or tracking location.

In any case, it is not necessary to fake the speed of light or achieve
Warp Speed Factor 1 or exploit the higher dimensions of String Theory :-)
to mount a relay attack againt time-of-flight distance bounding.  One
can instead attack the transmission channel as described in
http://www.rfidblog.org.uk/Hancke-Wisec2008.pdf <http://www.rfidblog.org.uk/Hancke-Wisec2008.pdf> .

Francisco

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