At 13:57:31 on 22/12/2005, Palindr?me delighted uk.finance by announcing:
There's no such thing. When the correct PIN is presented to the card, it responds with a cryptogram indicating the status. This cryptogram is generated using the private key stored on the card.
In article , Alex writes
IC Data
It may respond to the outside world with a very secure protocol but what goes on at gate level within the silicon is another matter.
But I expect that you are right, they would have thought about the possibilities of such an attack.
At 15:36:14 on 22/12/2005, Palindr?me delighted uk.finance by announcing:
I believe what happens is that the received PIN is encrypted and compared with the stored encrypted PIN. If the two match, a cryptogram so indicating is generated based on the transaction details. I guess that any attack would therefore have to be dynamic - quite impractical given the potential reward.
Not necessarily dynamic, IMHO. The stored encrypted PIN is presumably always stored in the same physical location. It could be zapped to a known state. If the received encrypted PIN is always stored in a pre-allocated fixed location before being fetched for comparison, it too could be zapped to a known state. Even if the comparison flag was only kept within the processor, which it may not be, the comparison flag may always end up set and the encrypted packet sent. Any PIN could then be entered and would be accepted.
It may be down to the program author. Having got in a received PIN and encrypted it, the author may have decided to write the thing to somewhere where it can be used again - before it is used, just in case it is needed more than once. For example, as part of the PIN changing routine.
I am, of course, not saying that this is the case or that any such attacks at the internal physical layer would succeed or be cost effective.
However, someone simply smashing the case open and directly accessing the hard drive is something that many computer security experts seem to have failed to consider, in the past.
Bugger! I knew there was a reason for not leaving my purse in my hand luggage and letting it go through the airport security scanner.
I never know what to leave in or take out. As they always seem to want to open *my* bag, no matter what I have in it, I seem to be going through a phase of having to use three trays for my keys and other stuff..And they *still* find something suspicious - but get dead officious if I try to get out of them, "Why me and my bag?"
It only seems to be men.. perhaps you are all born with built-in Audabe sensors..;)
I believe there was a paper around that iirc suggested a rogue bank /insider/ might expect to guess in around 16-20 attempts on average, rather than 5000, because of weaknesses in the system. Anyone confirm this please?
Alex wrote: ...
For 3 attempts per card at one of 10000 PINs, the chance of cracking a given card is 3 in 10000 (I think this is discussed elsewhere).
The chance of cracking /at least one/ of 10 cards, assuming the PINs are unrelated, is then 1 - (1 - 3/10000) ** 10, or about 0.002996. Say 1 in 300.
In message , Tumbleweed writes
AIUI such a cloned cards would fail at the ATM.
Alex wrote: ...
OK then, what possibilities are there should a corrupt bank employee provide the bank's key(s) to his corrupt mates?
That was for the old algorithms used in storing the PIN. It doesnt apply to C&P.
Yes, of course. But the /only/ valid signature is one /the cardholder/ has signed. A forgery is just that. So in principle the cardholder merely proves he was elsewhere, and therefore /he/ cannot have signed the slip, and therefore it /must/ be a forgery and therefore invalid. Furthermore, the bank does /not/ have any defence in saying the cardholder failed to keep the signature "secure".
With a PIN it simply isn't the same. Since the cardholder is /supposed/ to keep the PIN private, then a priori if someone else knows it, the cardholder may be accused of negligence or complicity; nor is there any possible defence in being elsewhere. (Imagine a company safe, if you will. The big boss shall we say, is the only one with the combination. One weekend, CCTV shows an intruder operating the lock, and the jewels within being taken. Who do you suppose will top the police's interview list?)
Tim wrote: ...
Sorry, but I have seen a bank rep saying these cards are /totally/ secure and foolproof. Which is exactly why I am worried about such cards.
At 18:00:42 on 22/12/2005, Mike Scott delighted uk.finance by announcing:
How does the employee get the key(s)?
At 18:00:59 on 22/12/2005, john boyle delighted uk.finance by announcing:
Or even to cards issued within the last decade or so; ever since the capability to change PIN was introduced.
Well, I bet they have some pretty strict version control on the software that generates the pseudo-random PINS, to make sure that there is no "accidental" link to the card numbers..
Turning up in your new roller might not be advisable.
At 18:55:06 on 22/12/2005, Palindr?me delighted uk.finance by announcing:
But we're talking about keys, not PINs.
No I am not. Whether they do or do not use the same PIN makes absolutely no difference whatsoever to the odds.
Choose a different random number to try for every attempt. With 10 cards you get 30 attempts. Therefore the chance of getting at least one attempt correct is 30/10000. Those odds are totally independent of whether the cards use the same or different PINs - or indeed if the card were to change its PIN after every attempt.
Of course, if you *do* get the PIN correct on any attempt, it would be a good idea to try that same PIN on all the remaining cards in case any of them have the same PIN.
Well, someone has had to write and to maintain the software used to generate keys as well. And arguably they are more useful than the PINs as they presumably outlive PIN changes. But it would be a lot harder to make use of the keys than the PINS - even allowing for the number of people that change PINS on receipt.
It would be a laugh if all cards from one ccc went out, for a day with the same PIN by mistake..due to a software glitch, say.
The "OK" signal is not on a physical dedicated data line anywhere. It will be a data message generated by the on-chip processor under firmware control. You cannot alter the program by physically altering the chip.
Yes, physical security has been addressed AFAIAA by means of encapsulating the chip in a way that would not make it easy to get to the surface of the silicone.
Cloning or altering the chip's hardware would be of no use to the forger. The information that needs to be changed is the data contained in what is effectively read-only memory (either data or program memory). Which in essence is the presence or absence of a charge in a microscopic memory cell.
It *is* possible to read and change charges in such cells by means of an external device, and blueprints are not likely to be needed as a memory array is pretty obvious on a chip. But not only does that take so long to set up that you would not be able to compromise many cards in a day, but anyone who can afford the equipment to do so is unlikely to find it worthwhile to risk being convicted of a serious crime to commit such fraud, and people who work in places where they might get the occasional access to such equipment would not be able to compromise enough cards to cause much damage.
Technology advances, and there may well come a time when the necessary equipment *is* affordable - but by that time I should think the security measures will have been updated to suit.
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