Building a hacker-proof network

By Arik Hesseldahl

updated 4:16 p.m. ET April 5, 2005

In Cambridge, Mass., not too far from the Charles River, which cuts near Harvard and M.I.T., David Pearson is attempting to build an un-hackable network.

Pearson is a division scientist at BBN Technologies, a private research company in Cambridge, Mass., which is most famous for building, in 1969, the first few nodes of a computer network connecting its headquarters to Harvard University and Boston University that over time would evolve into the Internet. Now the firm has built a network it says is impervious to hackers.

"If someone is eavesdropping, they introduce errors into the communications," Pearson says. "If that happens we just throw the keys away and start over."

For decades, public networks have done a fair job of protecting most sensitive communications from all but the most determined efforts to crack them. But the field is changing quickly. Looming on the horizon is the threat of quantum computing, which one day will render conventional data security algorithms obsolete.

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Replace transistors (the heart of today's silicon-based computers) with electrons (used in quantum computing) and you can build a computer capable of breaking today's strongest cryptosystems in a matter of hours or even minutes. That's because quantum computers process information orders of magnitude faster and, therefore, can unscramble encrypted data much, much faster.

The answer is quantum cryptography, which harnesses quantum physics to create encryption keys that are all but impossible to crack because they are rendered useless by simply looking at them. Data using those keys is simply resent using new keys.

In the physical world, objects are measured precisely, by size, location and destination. At the quantum level where objects are infinitely small, it's hard to measure particles like electrons and photons in the same way. The best you can do is predict their behavior and properties based on probabilities, hence the uncertainty.

As it turns out, this uncertainty is helpful in making encryption keys, which are used to weave complex mathematical algorithms that scramble sensitive data and make it look like gibberish to anyone without a key. It's possible to create a set of keys that will be rendered useless if a third party even looks at them. This methodology results in sky-high barriers against eavesdropping. It gets even higher when you create a new key for every single packet in the data stream.

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