Chip and PIN is broken, say researchers

Chip and PIN is broken, say researchers

Summary: A flaw in the protocol underlying chip-and-PIN transactions allows an attacker to push through a purchase without a valid PIN

TOPICS: Security

Chip-and-PIN readers can be tricked into accepting transactions without a valid personal identification number, opening the door to fraud, researchers have found.

Researchers at Cambridge University have found a fundamental flaw in the EMV — Europay, MasterCard, Visa — protocol that underlies chip-and-PIN validation for debit and credit cards.

As a consequence, a device can be created to modify and intercept communications between a card and a point-of-sale terminal, and fool the terminal into accepting that a PIN verification has succeeded.

"Chip and PIN is fundamentally broken," Professor Ross Anderson of Cambridge University told ZDNet UK. "Banks and merchants rely on the words 'Verified by PIN' on receipts, but they don't mean anything."

The researchers conducted an attack that succeeded in tricking a card reader into authenticating a transaction, even though no valid PIN was entered. In a later test, they managed to authenticate transactions, without the correct PIN, with valid cards from six different card issuers. Those issuers were Barclaycard, Co-operative Bank, Halifax, Bank of Scotland, HSBC and John Lewis.

The central problem with the EMV protocol is that it allows the card and the terminal to generate ambiguous data about the verification process, which the bank will accept as valid.

In particular, the terminal can record that a PIN verification has taken place, while the card itself receives a verification message that does not specify that a PIN has been used. The resultant authorisation by the terminal is accepted by the bank, and the transaction goes ahead.

This means that while a PIN must be entered, any PIN code would be accepted by the terminal, the researchers said in a paper entitled Chip and PIN is Broken.

The researchers said the engineering and programming skills necessary to make a man-in-the-middle device to conduct the attack are elementary.

"The attack doesn't require too much technical skill [to emulate]," said Steven Murdoch, who took part in the Cambridge University research, alongside Anderson and Saar Drimer.

Behind the attack
The attack targets the way the various security mechanisms interact in the cardholder verification process. In this process, the chip in the card and the terminal decide how to authenticate the transaction. The cards examined by the researchers all recognised as authentication, in descending order of preference: PIN verification; signature verification; and no verification.

The majority of transactions require PIN verification. The customer enters their number on a PIN entry device. The PIN is then sent to the card, which compares it to a PIN...

Topic: Security

Tom Espiner

About Tom Espiner

Tom is a technology reporter for He covers the security beat, writing about everything from hacking and cybercrime to threats and mitigation. He also focuses on open source and emerging technologies, all the while trying to cut through greenwash.

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  • Typical crummy industry response...

    Surely, they could have managed something like:

    Fortunately, the hardware rig and access is pretty difficult to set up for the average card thief, even when you've figured out how to do this. For this reason, this flaw hasn't yet caused a major problem.

    But the Cambridge researchers do appear to have stumbled across a blatant and embarrassing flaw in the protocol, which has the potential to cause real damage. Therefore, it would be a good idea if we took some reasonably urgent action to correct it. We'll get onto it straight away.

    But no, that isn't the sort of honesty level that our industry finds acceptable...
  • To true.

    Indeed very well put, besides it's only a matter of time before some one reduces the means to a fake card, and then they can move onto cracking the wireless cards.

    Oh and I like the way the end user gets left to pick up the financial peaces after the purverable hits the fan.
  • Chip and pin is broken

    This is an excellent article - many thanks
    Shibley R
  • No evidence this scam is happening?

    Good company response - if the whole world believes everything they hear! What about the thousands of people who lost money only to be told that they MUST HAVE "leaked" their PIN? There are loads of people who reckon they never let anyone get their PIN but still bogus transactions are blamed on them with lines like: "You maybe even let someone see the buttons being pressed at the ATM or Tesco's till."

    If PIN authentication is done locally rather than by a secure database transaction, then there is absolutely no way whatsoever that anyone can say this scam hasn't been perpetrated.

    So if you lose your card or if it gets cloned in a swipe pass, it turns out it's no safer than any of the old type. How do you feel now?
    Fat Pop Do Wop
  • chip and pin not broken, UK Banks that Issue Cards are.

    Calling EMV broken is laughable. First EMV supplys a variaty of options that are scalable in complexity and security. For example SDA, EMV covers the possibility of a static authentication, is it safe? not realy. Replay attacks are super easy.
    About the attack this guys use. DDA, that means dynamic authentication ,where unlike SDA the cryptogram is not static, meaning that replay attacks are not possible. HOWEVER it does not prevent WEDGE attacks or man in the middle, whatever you want to call it. This DDA weakness, as the SDA weakness are documented, reading it right now in one famous card issuer company (TOP3), that even don't allow cards issued with DDA and SDA , this document is 4 years old.
    There is a 3
  • CHIP and SPIN

    It amazes me that everyone argues over the (usually technical) detail without ever mentioning the much bigger flaw in the Chip and PIN system. Four digits, or any number of digits for that matter, are simply not a reliable mandate. They are not inextricably linked to the individual. Any person or any device that comes up with the numbers, or their abstracted equivalent, can authorise the transaction. How can that possibly be a reliable manadate?

    Try proving you didn't look after your PIN to a bank who has lobbied to get legislation on its side and is determined to cut it's losses through fraudulent use. Then you see the whole point of the system - it is your loss now not the banks.

    Even more staggering is they say it was an authorised transaction based on their secretive assessment so, therefore, you didn't look after your PIN. Try proving otherwise.
    Mr Simple
  • The reason it is taking so long for EMV cards to come to the U.S. is that credit card companies have been willing to tolerate mag-stripe related losses. Switching to EMV would cost U.S. issuers about $3 billion, according to one estimate, and merchants would have to pay not much less to upgrade their point-of-sale equipment.

    Now that Visa has made it mandatory for all U.S. processors to support acceptance of chip-based transactions by April, 2013 (, the dynamics have changed completely. The banks have no option but to build the infrastructure, so once that's done, they might as well start using it. After all, if the U.K. chip-and-PIN experience is anything to go by, switching to it would result in hundreds of millions of dollars in savings from lower fraud losses. U.S. banks would certainly take the windfall if it comes their way.