Crypto boffins: let's get physical

Researchers at MIT have developed a physical token, based on tiny glass spheres encased in epoxy resin, as a more secure alternative to generating cryptographic keys electronically.

With computers getting ever more powerful, especially when quantum-based technology come on the scene, some predict the mathematical algorithms which underpin current encryption techniques could be broken.

Such computers may be capable of factorising the product of very large prime numbers, but would struggle to unravel a one-way function based on a physical token. So the theory goes.

The MIT boffins created a physical one-way function by connecting cryptography with mesoscopics, the study of how waves travel in disordered materials.

In the September 20 issue of Science they show a simple token (costing pennies) made of tiny glass spheres in a clear epoxy containing around one trillion bits of data in the locations of the spheres.

Laser light shined on the token produces a speckle pattern, which is then recorded and used to generate a cryptographic key. Terminals (smart card readers, for example) can send this key over a conventional communications channel to identify and authenticate a token.

The researchers believe this new approach will improve information security on the Internet and elsewhere.

They believe it is technologically unfeasible to duplicate the epoxy resin. Also an enormous number of different keys can be produced as a function of how the laser reads it.

The data is stored in a material, rather than in a circuit, which means that the technology can also be used as part of a device that needs authentication, such as a security sensor, and is more tamper proof.

The low cost and tamper-proof characteristics may lead to applications in everyday objects such as envelopes and bank notes, the researchers predict.

"These capabilities are all of great interest to the cryptographic community," says Neil Gershenfeld, associate professor and director of the Center for Bits and Atoms at MIT, who led the work. "The introduction of physical one-way functions provides a new tool for them that promises to help make information security more accessible and more reliable." ®

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New approach to secure digital information developed at MIT