Flaw in Google Wallet PIN Security

Friday, February 10, 2012 @ 04:02 PM gHale

Google Wallet’s PIN protection is open to a brute-force attack that takes seconds to complete.

The attack can occur when physical access is available, or the phone has been previously “rooted” by the user. Once the assault succeeds the attacker can read the contents of the wallet including credit card numbers and other details such as the transaction history, said a researcher at categoriser zvelo. The problem can escalate because Google can’t fix the flaw without shifting responsibility for the PIN onto the banks, who might not want it.

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Google Wallet uses Near Field Communications (NFC) a wireless technology so the user can make payments. The Google Wallet provides a management interface to the cards stored on the system, and the hit triggers an encrypted exchange of information between the card and the till authorizing the payment.

That exchange remains secure, but when the user wants to edit their card details, or see their transaction history, they use Google Wallet which requires a 4-digit PIN, and that PIN is vulnerable, zvelo said.

The wallet application stores a hash of the PIN, and it is possible to create a matching PIN simply by hashing all 10,000 possible numbers — a process which only takes a few seconds as zvelo demonstrated on a video.

The hash files, accompanied by other data warranting further inquiry, are only available to other applications once a user roots the handset — the Android OS keeps applications separated so this attack can only occur on stolen phones or those rooted by their owners. The latter case could occur through a rogue app that could lift all the data remotely without the user being aware.

The problem for Google would be to fix this is to move all the data into the secure element on the phone. The secure element is essential to NFC transactions, but falls under the legal responsibility of the payment processor — so moving the PIN into there would change the already complex legal architecture.

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