A Quantum Leap in Cryptography

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Chip Elliott, principal engineer with the Cambridge, MA-based BBN, says they've created a so-called "free-space" quantum cryptography network that can send quantum keys, or encrypted communications, about 15 miles using telescopes lined up at each point, without optical fiber. 

Applying the same technology, companies could send quantum-encrypted communications back and forth using a satellite. Elliott says that while free-space quantum cryptography is not as far along in development as the "wired" variety, the systems will be easier and cheaper to implement, since the necessary components are less expensive. He says there may even be free-space encryption products available to businesses and governments by year-end.

Ray Trygstad, assistant director of information technology for the Rice campus of the Illinois Institute of Technology in Wheaton, IL, is more enthusiastic about the potential for free-space quantum cryptography than systems that use optical fiber. Ultimately, he sees free-space as a preferred way to secure pay television or classified telephone calls, or, in the nearer term, for companies to provide truly secure wireless access to employees on their corporate campuses.

Since "wireless security is traditionally very weak," Trygstad says, "coupling free-space quantum cryptography with WiMax could provide more of a benefit."

It appears that quantum cryptography has moved from scientists' blackboards to board rooms faster than even many keen observers thought possible.

Still, challenges remain. Trygstad believes that in the next few years, only a few high-end financial firms and government agencies may use quantum encryption to secure their most sensitive information, since the cost is still relatively high -- around $100,000 for two points of connection. Many enterprises may opt to use those security budget dollars in other areas that are more at risk.

But, Kessler argues in his research, financial services firms, in particular, should be considering the use of quantum cryptography, since breakthroughs are currently happening in the mathematical world that could substantially weaken computationally based encryption schemes, like RSA. One major example: mathematicians may be on the verge of proving the Riemann Hypothesis, which outlines how many prime numbers exist below a certain value. If proven, Kessler reasons, a person could figure out the factoring behind an RSA encryption scheme in fewer calculations.

Distance also continues to be problematic for quantum cryptography. Since its keys cannot be measured or tampered en route, traditional kinds of "repeaters" don't work -- so most quantum systems can only relay data between two encryption appliances between 100 and 150 kilometers.

"These distance limitations are continually improving with better photon generation and fiber optics as well as better overall transmission technology," says Kessler, "but distance remains the most limiting element of quantum key distribution."

Some users can overcome the issue by linking together systems, so essentially the information is decrypted and re-encrypted at each point along the way. Also, Gelfond maintains that for a lot of his customers the distance limitation is not an issue because they're transfering and securing information "within the metro core" -- between a main office and a back-up site that may be just a few blocks, or floors, away. 

Shields and Ribordy say that "quantum repeaters" are being developed, and Shields believes they may be a reality within five years. While most companies wait for the costs to come down, and the technological challenges to be ironed out, early movers like MagiQ, id Quantique, and NEC still see the opportunity in the commercial market.

"Some organizations understand that communication of the most sensitive data warrants the highest security possible," says NEC's Nakamura, "and will allocate appropriate budgets to ensure this. We see this type of high-end user as representing the main initial market for quantum cryptography."