Alice and Bob make wireless temperature sensors that run a 6tisch stack.
Charlie owns a nationwide chain grocery store and is rolling out 6tisch
everywhere.
Zelda sells wireless toys that use 802.15.4e.
Mallory is always lurking.
Charlie needs to decide if and how to use message integrity checks on
enhanced beacons.
He thinks that he has three options:
1) don't use MICs on EBs.
2) use MICs on EBs, with a secret key
3) use MICs on EBs, with a well-known key
Charlie does some testing of option 1, and finds that when there is a
Zelda's Toy Shop
near one of his stores, his networks take a *really* long time to join.
It seems that
Zelda's toys send 15.4e EBs too, and they send a lot of them. The
sensors that
Alice and Bob sell spend a lot of time and battery energy trying to join
the wrong network.
Charlie would really like something better than option 1.
Charlie decides to use option 2, a MIC with a secret key, and it works
great! The sensors
ignore EBs from Zelda's, and only respond to EBs from his networks. He
asks Alice and Bob
if they are willing to install that secret key before they ship the
sensors to his various
stores, and he's such a big customer that they say sure. He is driving
an industry standard.
But then Charlie gets worried. He's probably going to end up buying
sensors from
Aaron, Abu, Acacia, and Ada as well. How will he keep his key secret?
Eventually
someone will find it or leak it, and then there will be a big news story
"Charlie's
Markets Hacked!" He imagines himself trying to explain to reporters
that the
MIC key on the EB is just there for network segregation and message
integrity.
He imagines that wouldn't go very well, so he decides option 2 is out.
Maybe
he can just publish the MIC key in the standard?
But if Charlie uses option 3, a well-known key, Mallory will be able to
spoof EBs.
Of course, if he uses no MIC at all, Mallory will also be able to spoof EBs.
What should Charlie do?
ksjp
_______________________________________________
6tisch mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/6tisch
