60,000 Oyster Cards Corrupted - Smart Card News

So what on earth is going on here? Two major outages within two weeks both due to the
transmission of ‘incorrect data tables’ to all the Oyster Card Terminals, is such an
accident possible or is there something more going on behind the scenes?
We have been reporting in SCN this year of the breaches in the security of the Mifare
chip which is the platform used by the Oyster card. In January we reported on the
discoveries of Karsten Nohl (University of Virginia) and Henryk Plötz who effectively
publically revealed much of the cryptographic architecture at the core of the Mifare chip.
In March we revealed the work of the digital security group at Radboud University in the
Netherlands who carried on with where Noel and Plotz left off. There can be no doubt
that both teams had cracked the Mifare Crypto-1 algorithms and last month we reported
on the Radboud team travelling the London Underground for free.
It gets worse because NXP (nee Philips Semiconductors) who own (Mifare is proprietary
technology) and manufacture the Mifare chips have now lost a ruling in the Netherlands
to block the Radboud University team from publishing their results. Mifare is now used
in up to a billion smart cards in mass transit and physical access control applications.
Nobody doubts that it will take years and significant costs to fix the problem which
means changing the cards, the smart card readers and some of the software middleware
that handles the application on the card. Involved in all of this is the cryptographic key
management, let nobody fool you, this needs to be changed as well.
If you were Transys the first thing you would try to do is to enhance the application
security around the use of the smart card. You can’t do anything about the cryptography
because that is deeply buried in the chips and can’t be changed (without changing the
chip). So the next best thing is to try and detect counterfeit cards or even authentic cards
where the data on the card has been manipulated. Can you imagine somebody selling a
kit for Oyster card users to reset the value on their cards, this is effectively what the
Radboud University team demonstrated in London.
So more about those ‘incorrect data tables’ what could that mean? Now as far as I know
the cost of the journeys on the London Underground have not changed for some time and
certainly not in the month of July so it’s not obvious that there would be any changes
here. But how about hot card lists? At the end of the day software on the Transys servers
could examine what the cards are up to, and notice everything seems to be linked to pay
as you go, which has a weaker registration system? If cards were being manipulated then
it should be possible to detect this back at base which should have a record of value loads
and spends. Each Mifare card has a unique (well its supposed to be although there have
been reports of duplicates) ID number which would be more difficult for the home user to
change although given the attacks reported previously any thing else relating to the
Oyster card application could be changed. With all this information Transys could send
out hot card lists to disable these suspect cards, this is what appeared to happen on the
first system failure. As an alternative you could just refuse access to the suspect cards on
the hot list and that perhaps is what happened on the latest system failure.