Now, 'Inkblot' Passwords For Unbreakable Security


These puzzles would prove significant when security breaches of websites result in the loss of millions of user passwords - a common occurrence that has plagued such companies as LinkedIn, Sony and Gawker.

These passwords are stored as cryptographic hash functions, in which passwords of any length are converted into strings of bits of uniform length.

A thief can't readily decipher these hashes, but can mount what's called an automated offline dictionary attack.

Computers today can evaluate as many as 250 million possible hash values every second, Blocki noted.

Given the continued popularity of easy passwords, such as "123456" or "password," it's not always difficult to crack these hashes. But even hard passwords are vulnerable to the latest brute force methods, Blocki said.

Given the continued popularity of easy passwords, such as "123456" or "password," it's not always difficult to crack these hashes. But even hard passwords are vulnerable to the latest brute force methods, Blocki said.

In the case of a GOTCHA, however, a computer programme alone wouldn't be enough to break into an account.

"To crack the user's password offline, the adversary must simultaneously guess the user's password and the answer to the corresponding puzzle," Datta said.

"A computer can't do that alone. And if the computer must constantly interact with a human to solve the puzzle, it no longer can bring its brute force to bear to crack hashes," said Datta.

Because the user's descriptive phrases for inkblots are stored, users don't have to memorise their descriptions, but have to be able to pick them out from a list.

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Source: PTI