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For
Online Security, Users Have To Match Inkblots With Text Phrases Entered By
Them
Washington: Scientists, including one of Indian-origin, claim to have
developed a new ‘inkblot’ password system that could provide
near-unbreakable layer of security against online password thefts.
The new password system called GOTCHA developed at
the Carnegie Mellon University could secure high-value information such as
bank accounts — even if the password leaks as part of a large-scale site
breach.
To create a GOTCHA, a user chooses a password and a
computer then generates several random, multi-coloured inkblots.
The user describes each inkblot with a text phrase.
These phrases are then stored in a random order along with the password.
When the user returns to the site and signs in with the password, the
inkblots are displayed again along with the list of descriptive phrases;
the user then matches each phrase with the appropriate inkblot.
“These are puzzles that are easy for a human to
solve, but hard for a computer to solve, even if it has the random bits
used to generate the puzzle,” said Jeremiah Blocki, who worked on the
system along with professor Manuel Blum, and Anupam Datta, associate
professor of computer science.
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. In the case of a GOTCHA, however, acomputer 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 memorize their descriptions, but have to be able to pick them out
from a list. PTI
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