Hello,
I have been following this list for some time, and I wanted to comment
on one of the projects I'm working on, just to hear your comments about
it (and because I think is quite interesting for its security
implications...).
Starting on August 2009, all new Brazilian vehicles will need to include
a mandatory anti-theft device, installed from factory, that will be
activated on demand by the vehicle owner. The device (TCU) will connect
with an owner selected service operator (SO) by using a standard
protocol defined by the National Department of Traffic (DENATRAN),
closely based on Motorola's ACP protocol, over GPRS. The main functions
of the anti-theft device are vehicle tracking, and remote blocking of
the vehicle by the service operator on request of the owner or of the
police department.
As you may notice, the risk of not implementing this in the right way,
are enormous. Not only because of privacy concerns, but because anyone
could just block/unblock your car engine or doors remotely, and
massively (think hundreds of thousands cars in some SO). In my present
opinion, there's no way they are going to do it correctly.
One of the issues is how the TCU will be activated. The idea is the the
owner will be able to switch SO whenever he wants, and for that an
activation protocol is needed. The current 'high-level' proposal by
DENATRAN is here
http://www.gristec.com.br/disco_virtual/SMS_Proposal_ACP_245.pdf
In few words, there's a default authkey installed on every device, and a
'secret' key for each SO. When a SO needs to activate a device, it sends
an SMS message to the TCU so it connects to the SO server through GRPS,
then the SO configures the TCU with it's authkey, and from that point on
the TCU only answers messages that include that authkey. To change to
another SO, the current SO sends a message that sets the authkey to the
default one, and repeats the process.
I can think of many of ways to defeat an scheme like that (from just
getting the SIM card from the TCU and playing the protocol against the
SO to get it's key, eavesdropping some weak point, replaying SO->TCU
commands, etc.).
The reasons of why they say the proposal is OK are based on assuming: a)
the secrecy of the SO authkey, which is sent in clear to every activated
device b) the secrecy of the ICC-ID associated to each phone number (at
least to do something massively), which is known by, at least every, SO,
c) the security of the network (TCU->(GRPS/GSM)->Telco->(VPN)->SO to
avoid eavesdropping/spoofing, which is compromised by any compromised SO).
My company started to participate on the working groups that are trying
to define all the technical and process issues of the regulation, and
I'm personally deeply concerned. We are not security experts (though we
build the tracking units and develop it's firmware and server side
components), but we want to contribute as much as we can to the process.
Do you know of any similar experiences we can base on? Do you think this
is doomed to fail? Am I being too paranoid and things are done this way
normally and attacks 'just don't happen';)?
Any comment is welcomed! Thanks!
--
Santiago
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