Subject: [core] Loading a sensor's identity and other bootstrap data

From: Robert Moskowitz <[email-masked]>
Date: Fri, 23 Mar 2012 09:52:23 +0100

I am not an engineer and I do not know if anyone has patented this 
approach...

The cost of loading identity information has to be weighed against the 
cost of a device without (if credentials are stolen is it cheaper to 
just by new?).

Under water/acid/oil proof glue are two contacts.  This glue can be 
removed with a razor blade, and the contacts shorted out.

Once shorted out, for N seconds the sensor will accept a datagram with a 
key pair, perhaps an ECQV random secret, and other special bootstrap 
data.    This needs to fit into one 127 byte frame (unless it is 15.4g 
capable).  Perhaps the sensor will only allow this operation M times.

So you work for an organization that doesnt' trust outsiders with its 
security, even its vendors.  Or you had just pulled a door lock out of 
your neighbor's garbage.

So you scrap off the glue, put the sensor and your PC (with 802.15.4 
adapter and special bootstrap loading software) into a faraday cage.  
With probes in the cage, you short out the contacts, and press the enter 
key on the PC.  Tada!  New credentials in the sensor that you set!  Take 
stuff out of the cage, and put fresh glue over the contacts and install 
the sensor in your network.

If you live out in the countryside you can forego the faraday cage.  ;)

An alternative approach with a sensor that is powerful enough to gen 
keys and have a really good PRF:

On shorting out the contacts, the sensor gens up fresh identity, random 
ECQV secret, etc. then sends them out at low power (but not the private 
key!).  More secure; faraday cage is optional.  But you need to trust 
the manufacturer in its ablity to perduce good key pairs and random 
numbers.  Plus pay for the computing functionality on each sensor.

Just sitting here in the KLM lounge in Schipol waiting for my friends to 
get home to go there for the Sabbath.  Got to keep the mind busy on 
things other than real work and committed writing assignments!