Comment by furyg3 | Hacker News Reader

Comment by furyg3 | Hacker News Reader

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I'm guessing it's:

a) RFID is readable from further away than they'd like you to think.

b) You don't know when your RFID card is being read.

c) Points a and b make tracking you really easy... for anyone to do.

d) The only thing that should (ideally) be stored on any RFID chip is a unique number... not any history (recent transactions), personal data (name/phone/picture), or payment system (think public transport) where the actual info about how much money is on the card is stored on the card itself... but that's exactly the type of information which is stored on these cards.

e) Nearly all encryption mechanisms are shoddy, either because they're poorly implemented open standards, or developed in-house by the vendor (security through obscurity). Cards that make use of real encryption would be (are?) expensive to make.

Here in the Netherlands the entire public transit system is being switched to an RFID-based system, and even to a non-security expert (me) it's clear that the system is based on an insecure premise (d), and would be very vulnerable to unknown scanning by someone wishing to track you from a decent distance (a-b-c).

I was interested in the security of this system, and found this video (http://events.ccc.de/congress/2007/Fahrplan/events/2378.en.h...) of some hackers who did an amazing job tearing it to shreds. They're pretty adiment that nobody is doing adequate encryption on RFID cards. If you're interested in this at all it's an amazing hack, involving dissolving the cards layer by layer to see the code.

a) it's a radio signal. However low power it is, it gets transmitted huge distances while still being detectable (especially if you capture it multiple times to read through noise). I'd love to take a massive dish (say, 20 foot diameter) & see how many can be captured from inside a neighboring building.

b) I have yet to hear of a single RFID card which has a switch on it to address this. It's a big security problem. I saw one hobbyist hook up an OLED pixel, but that's it.

e) I've heard of a couple, very expensive, challenge-response and public-key RFID systems. That is acceptable for authentication, but I've never heard of them actually being used, and one or two were only proofs-of-concept, IIRC. Many (I'd say easily most in use, from what I gather) simply transmit a unique ID, that never changes, which is used to perform X, which is ridiculously insecure.

  > I'd love to take a massive dish (say, 20 foot
  > diameter) & see how many can be captured from
  > inside a neighboring building.

Are you talking about active or passive RFID? I was under the impression that most RFID in use is passive. In that case, you'd have to transmit something to get a response, unless you're talking about camping out in an area where lots of cards are going be activated by various things other than yourself (e.g. entrance to the transit system). But even then the transmitting power of the RFID chip is proportional (?) to the power used to activate it, so something that only expects to read it from 2 feet away isn't going to blast it with enough power to be reliably read from 100 feet away, unless I'm misunderstanding how people do those long distance RFID reading records...

Passively camping out. Lots of (questionable) RFID uses I've seen are to unlock doors, often external ones. And if it's in a business park, it could easily be closer to 50 feet or less between buildings.

So say a 5-foot range. Find a group of employees out for lunch together and I walk past the table with a backpack on. Hardly suspicious, and I've probably got most of their building access cards.

I was responding to someone to someone talking about a 20-foot dish though. That's not something you stuff in a backpack. I was commenting on his desire to listen with a huge dish at a distance.

I vaguely remember an article from around the time RFID passports were a hot issue, in which researchers used multiple capturing devices and were able to square the reading distance. I don't know whether that was specific to the distance they used, the type of RFID, or even an upper limit, but it was an unbelievable improvement.

Most applications of RFID by authentication (think door locks) use only unique ID (address) of the card and nothing else. And the communication protocol used by reader works like this: Is there anyone with address starting with 0? ... Starting with 1? Yes. Starting with 10? ... Starting with 11? Yes. ..... So you only have to listen to reader side of communication and guess the last bit.

When I first heard of this attack I'm pretty sure the solution to that is a high-gain antenna. I don't know how often that actually works, but it's theoretically supposed to.

Imagine how many you could collect on your way to and from work each day in heavy traffic?

I'd love to take a massive dish (say, 20 foot diameter) & see how many can be captured from inside a neighboring building.

For active RFID, maybe you'd grab quite a bit.

You'd also grab quite a bit of noise. These are very low power signals; restricted by regulations in at least Australia, N.America, but it could still work. It did on 2005: http://blog.makezine.com/archive/2005/07/_defcon_rfid_world_...

An important note on the 69-foot record in 2005 you linked: they've just got two antennas, no focusing dish at all.

If someone comes along with a powerful rig, say using some of the techniques astronomers have had for many years to detect far weaker signals, what sort of distance might we be talking? It's not too far-fetched if you include possible corporate / governmental espionage attempts.

> d) The only thing that should (ideally) be stored on any RFID chip is a unique number

I disagree. This is basically where RFID has its benefits. Transport for London has the Oyster card, which I'm pretty sure is "electronic cash", i.e. your balance is stored on the card. This allows the system to work without the huge point of failure that is a central database and the connections to it. They have millions of people passing though thousands of checkpoints, many of them on moving busses. The infrastructure needed to make sure that every single one of these checkpoints can at any given time instantly run a transaction on the central database vs. having autonomous readers that just needs to upload their log every once in a while is huge.

It's basically the difference between mainframes/dumb terminals and P2P.

The problem is that RFID implementers have been cheap with the security on those chips. It's pretty simple to make a secure setup (famous last words....) tried and true ideas from cryptography (public key infrastructure etc..) but these call for more expensive chips, and when the choice is between expensive crypto that works and cheap security-through-obscurity that works until a grad-student is bored for the summer, you're going to go with the latter, of course.

Transport for London has the Oyster card, which I'm pretty sure is "electronic cash", i.e. your balance is stored on the card.

I wonder why people rolling out such systems never seem to see the obvious(?) writing on the wall:

1. Someone comes up with an "infinite balance"-hack.

2. Infinite balance cards are sold on a growing scale.

3. Transport company is forced to apply expensive bandaids to contain the problem.

Moreover I don't understand why they don't simply leverage the device that everyone already has in their pocket - the cellphone. The infrastructure would likely cost an order of magnitude less (barcode scanners like in airports, or bluetooth) and more importantly the system would be rather easy to make cryptographically secure because it's all in software.

"But what if I forgot my cellphone at home" - well, same thing if you forgot your RFID card at home.

> I wonder why people rolling out such systems never seem to see the obvious(?) writing on the wall:

The writing isn't at all obvious, otherwise they wouldn't have come up with it. I guess they've come to the conclusion that forging Oyster cash is similar to forging paper ticket or real cash. I don't know exactly how the Oyster card is implemented, but if it has some level of transaction log trail (however asynchronous), it's possible to detect forgeries (if you've only ever deposited £20, but since spend £100, you're cheating).

> Moreover I don't understand why they don't simply leverage the device that everyone already has in their pocket - the cellphone.

Scanning a barcode on a cellphone screen has three problems:

1: There are still loads and loads of cellphones not reliably capable of displaying a scannable barcode.

2: Barcodes are 100% copyable and include 0 cryptography - they have the same security as a barcode printed on a piece of paper, which, incidentally, is what they replace in airports.

3: A barcodes is read-only and requires online access to verify and record the transaction which is not feasible on the scale required for TfL.

Bluetooth has similar problems:

1: While most phones might be BT equipped, developing and supporting software for enough different phonemodels is very complex.

2: BT is designed for communication between specific devices, not a "class" of trusted devices. You can't trust all TfL checkpoints under one, so you'd have to navigate some sort of interaction every time you check in and out of a station/bus. Also, this interaction is different for each phone type = support hell.

3: BT is long range, compared to an RFID card. Sure, an RFID card might be skimmed from a difference, but it's easy for a reader to tell the card directly on the reader from every other card in the room. No so much for BT.

The solution including cellphones we need is NFC, which is basically RFID that can leverage the processing power of the cellphone. It just doesn't exist on very many phones yet.

Barcodes are 100% copyable and include 0 cryptography

That doesn't have to be case, which imho invalidates the rest of your points.

It's perfectly doable to issue tamper-proof tickets in the form of cryptographic signatures. So you could, for example, on a website order a barcode that encodes "This ticket valid between 10:00-18:00, on route section X, and belongs to Mr. John Doe". Obviously someone could copy and re-use that very barcode but you have the same problem with RFID tokens, unless there's some sort of centralized validation going on. Which is, btw, actually much easier to implement than you make it out to be, considering you'll have a hard time finding a train-station without GSM coverage nowadays.

I do agree with your concerns that not everyone has a phone capable of displaying these codes, yet, but it's a matter of years until that will be the case. During then you'll need the old paper tickets as a fallback - but that's the case with any new technology, it's not like you could flip the switch with RFID over night either.

Likewise Bluetooth may indeed be the wrong tool for the job, personally I'd favor the barcodes that seem to work out well enough on airports.

And finally, the development effort for making the software work all phone platforms is negligible. Again, the Airlines have demonstrated it can be done, and when you compare it to the effort required to rollout an RFID solution including the hardware then I'd bet the barcode approach is actually easier to do.

So. This, for once, is a problem that would be fairly straightforward to solve with technology. I can't help but assume this massive gravity towards more expensive and inferior solutions is mostly a result of lobbying. Obviously there's much more money to be made by handing out physical tokens and then enjoying the benefits of a ridiculously expensive support contract as you pile bandaid over bandaid...

Fair enough, I misunderstood how you imagined barcodes to be implemented, and yes, that invalidates my specific arguments.

I do, however, not agree that it's a superior solution to Oyster cards. First, the Oyster card was introduced in 2003 when even fewer cellphones would have been capable of displaying these barcodes - even then, the Oyster card was immediately available to everybody. That is a major feature - and it's not a small thing that even today all cellphones can't effortlessly do this. Fast mass adoption is a feature.

Also, no matter how easy the implementation, buying a barcode-ticket on your phone and then scanning it is more complicated than simply touching a card. If you have to run to catch a train, you don't want to have to stop and fiddle with your phone, for however short time, to get it to show the relevant barcode.

But that's dwelling over tiny details. My post was a counter-point to your claim that the Oyster card has grave and obvious flaws and was deployed in favour of an obviously better solution. I argue that, even considering that the Oyster card system have problems, those have not been exploited, while enabling the benefits of a pay-as-you-go system.

And just to be clear: I fully expect the Oyster system to be replaced by a system based on NFC once that is viable. That just wasn't in 2003, and it isn't today.

Hmm yea, you do have a point.

I admit I got a bit carried away on the barcode idea, mostly because I have used it at the airport and liked it. But I have to agree it might not scale as well to public transport use - the whole running after train thing.

Well, I guess we can meet in the middle and agree that NFC would be the near-optimal solution, when and if implemented securely (however unlikely that is.. ;-) ).

As far as I can tell, one large benefit for Oyster cards is that people can use the gates at tube stations faster than with paper tickets. This is quite impressive, given that an experienced commuter barely has to break stride to use a paper ticket. (And on buses, you don't have the delay of interacting with the bus driver - you beep on as you go past). I'm sure the cost savings for London Underground from increased speed beats that that they'll lose to forged Oyster cards.

but if it has some level of transaction log trail (however asynchronous)

"All transactions are settled between the card and reader alone. Readers transmit the transactions to the back office in batches but there is no need for this to be done in real time." - http://en.wikipedia.org/wiki/Oyster_card

People here are saying "I think/guess/assume that oyster cards work like... ". Without even checking with Wikipedia. I'd like to hear about the Oyster card system's strengths and weaknesses from someone who really knows the system.

This already has happened in Boston.

http://joshuamcginnis.com/2008/08/09/wow-how-to-hack-boston-...

It's really shocking that people think storing MONEY on a card that everyone has read/write access to is a GOOD idea.

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