Apr 242011

The passwords of the future could become more secure and, at the same time, simpler to use.

Researchers at the Max Planck Institute for the Physics of Complex Systems in Dresden have been inspired by the physics of critical phenomena in their attempts to significantly improve password protection. The researchers split a password into two sections. With the first, easy-to-memorize section they encrypt a CAPTCHA (“completely automated public Turing test to tell computers and humans apart”) — an image that computer programs per se have difficulty in deciphering. The researchers also make it more difficult for computers, whose task it is to automatically crack passwords, to read the passwords without authorization. They use images of a simulated physical system, which they additionally make unrecognizable with a chaotic process. These p-CAPTCHAs enable the Dresden physicists to achieve a high level of password protection, even though the user need only remember a weak password.

Computers sometimes use brute force. Hacking programs use so-called brute-force attacks to try out all possible character combinations to guess passwords. CAPTCHAs are therefore intended as an additional safeguard the input of which originates from a human being and not from a machine. They pose a task for the user which is simple enough for any human, yet very difficult for a program. Users must enter a distorted text which is displayed on the screen, for example. CAPTCHAs are increasingly being bypassed, however. Personal data of members of the “SchülerVZ” social network for school pupils have already been stolen in this way.

Researchers at the Max Planck Institute for the Physics of Complex Systems in Dresden have now developed a new type of password protection that is based on a combination of characters and a CAPTCHA. They also use mathematical methods from the physics of critical phenomena to protect the CAPTCHA from being accessed by computers. “We thus make the password protection both more effective and simpler,” says Konstantin Kladko, who had the idea for this interdisciplinary approach during his time at the Dresden Max Planck Institute; he is currently a researcher at Axioma Research in Palo Alto/USA.

The Dresden-based researchers initially combine password and CAPTCHA in a completely novel way. The CAPTCHA is no longer generated anew each time in order to distinguish the human user from a computer on a case-by-case basis. Rather, the physicists use the codeword in the image, which can only be deciphered by humans as the real password, which provides access to a social network or an online bank account, for example. The researchers additionally encrypt this password using a combination of characters.

However, that’s not all: the CAPTCHA is a snapshot of a dynamic, chaotic Hamiltonian system in two dimensions. For the sake of simplicity, his image can be imagined as a grey-scale pixel matrix, where every pixel represents an oscillator. The oscillators are coupled in a network. Every oscillator oscillates between two states and is affected by the neighbouring oscillators as it does so, thus resulting in the grey scales.

Chaotic development makes password unreadable

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