Robert Morris, RIP

To mark computer security pioneer Robert Morris' passing here is a puzzle he shared at his talk at Defcon some years ago

"This is a long term problem. If you work on it and make any progress against it, you'll find yourself much smarter at the far end, than you were at the near end.When I was in Norway about 5 years ago, I was there very close to the summer solstice. I was wandering around town at 2 o'clock in the morning and there was plenty of light out. You come to a sign that says New Minsk about 60 km and it points south.

And I ask the lady "what country is this?"

She scratched her head for a bit, and said "well I think its Norway"

I said "well who plows the roads?"

"well Norway does, but he have to pay them."

There is a triple boundary in this town that I was in between Norway, Finland and Russia.
But what I did there, was, I had a card about wallet size, I stuck it into a machine, I punched in four digits, and it gave me about 2,000 krone, whatever the hell that is.
Now there are a lot of participants in that transaction. When I put a card into that machine, punch in a pin, and it gurgles for awhile, and finally gives me, a fairly large amount of money. There are a lot of participants in that transaction. The bank that owned the machine that gave me the money, it gave some money away -- that bank wants it back. The pin is necessary to convince my own bank that I'm me. But I don't want my pin to be broadcast all over the world. My bank in the us, it hasn't really given out or taken in any money, really. But there is a lot of credits involved here. Somebody needs to charge somebody else for having more money available. Even though there was actually no cash transfer.

And the problem that I have in mind is

- who are all the participants in an ATM transaction?
- what do those participants need to satisfy their problems?
- how is that in fact done?

In a general way, does the atm system actually work in some reasonable sense? To which the answer is by the way: yes. The atm system damn well works. With extremely high reliability and accuracy. It surprises me. Its quite a bit different than voting machines.

Comments

[Sid Sidner]

I spent 11 years of my life thinking about ATM networks at ACI Worldwide, the last 5 as Director, Security Engineering. I also participated in the X9F6 working group, the U.S. standards body for payment card security.

I never knew Robert Morris cared about ATM security, or mused about it in the land of the midnight sun. However, I can relate: every time I use a card from my bank in Omaha, NE, USA, at some merchant in a place like Timsoara, Romania, and they cheerfully take it, I pause for a moment and marvel.

I have two observations to make about this, one commercial and one technical.

The reason this works commercially is a trust framework, just like the ones OIX promotes, run by the worldwide banking system. Just think about the complexities in international monetary settlement and fraud: consumer, merchant, network, or bank instigated.

The reason this works technically is some serious cryptography that mostly works, under sustained, well-funded attacks.

The ATM network used to use software cryptography. That is mostly gone, except from old gas pumps and backwater geos. In nearly all of the world, except for the U.S., this starts with hardware cryptography in the EMV cards used as consumer payment tokens and finishes with hardware security modules at the card issuance center and at the transaction authorization center.

Until we get to universal online identity tokens at least as good as EMV cards, we will never be able to do high value transaction on networks.

R.I.P., Robert Morris.

[Gregory Butler]

The irony is that the manufacturer of most US teller machines is (was) also the manufacturer of the notoriously-insecure and otherwise controversial voting machines: Diebold.

But I must imagine Mr. Morris knew that...