Quantum Cryptography on the Market Today

Classical Cryptography: Strengths and Weaknesses

Throughout history, important messages sent by governments, armies and businesses have relied on procedures to encrypt the messages by the sender which are then decrypted by the recipient. But to make this happen, information about the encoding, the secret key, must be shared by the sender and receiver. Thus prior to sending the messages, the sender and receiver must exchange the secret keys via courier or via a communications network. And if someone intercepts the secret key during its exchange between the sender and the receiver, all security of the encrypted message is lost.

Today cryptography adopts different techniques to exchange the secret keys or to encrypt messages, these are often called Public Key Protocols and are based on the use of very long prime numbers as secret keys. Two keys are involved in each encryption: a private key, which only the sender has access to, and a public key, available to anyone. The two keys work together, so a message encrypted with a public key can be decrypted only with the corresponding private key. Public key systems require that the sender knows the recipient's public key to encrypt a message.

A weakness of this system is that, in theory, given a powerful enough computer, it is possible to figure out the private key from the public key. As of today if the private/public keys are long enough, there does not exist a computer powerful enough to do this, but computer speed and advances in mathematical algorithms are very fast. Moreover, when Quamtum Computers will arrive, the situation will dramatically change.

Quantum Cryptography

A very active field in Quantum Mechanics is called Quantum Computations and the hope of the scientists working on it is to be able in 10 to 20 years to encode binary bits on particles like photons or electrons. Encoding binary bits in fundamental quantum particles will allow to build Quantum Computers which will be able to perform multiple complex calculations simultaneously and to solve almost istantaneously some mathematical problems which are practically impossible to solve with today computers. Among these problems, one is how to obtain a private key from the corresponding public key.

Another application of Quantum Mechanics is Quantum Cryptography, which is actually the application that is already very near to public use. Quantum Cryptography offers a new way, guaranteed by Quantum Mechanics, of generating and exchanging secret keys, an the good news that it is already on the market, well before Quantum Computers will be able to break the public/private keys.

Quantum cryptography allows the secrecy of the key to be guaranteed without the need to make any assumptions about the computing power of an attacker. It uses single photons, the fundamental quantum constituents of light, to transfer the numeric keys. Quantum physics dictates that if anyone or anything tries to spy on the photons' travels along the fiber optical cables, their encoded state will change. The sender and recipient will detect this interference and they will know that someone is tampering with the key.

Still some technical points have to be worked out. As of today Quantum Cryptography works only on limited distances, experimentally up to 150Km (latest result as of beginning 2004) and on point-to-point network. Moreover optical fibers have to be dedicated to this use. To be able to improve on the distance, quantum repeaters should be introduced, but research on them is still 5 to 10 years from commercial deployment.

Meanwhile, work is also under way in both Europe and the United States on a different way of carrying quantum bits. Researchers working separately in Britain, Austria and the U.S. national laboratories at Los Alamos, New Mexico, are experimenting with transmitting quantum keys through the air rather than over fiber optic lines. The idea is to send the quantum keys up to satellites and then down to another destination.

Commercial Interest

Quantum cryptography has already captured the interest of banks and intelligence agencies, as well as governments. For example, Visa International, the credit card organization, is already testing the technology. Other banks and financial institutions are considering Quantum Cryptography as a possibile substitute of Public Keys Protocols.

MagiQ Technologies, a New York company, and id Quantique, based in Geneva, have both recently started selling quantum cryptography products. Also larger players like NEC, Toshiba and Hewlett-Packard are saying that they are getting closer to introducing products.

The cost of deplyoment of a Quamtum Cryptography system in a large company network could be several hundreds of thousands of dollars (euros), and for the moment is limited to campus and metropolitan areas, but this will change fast as soon as the technology becomes more mature.

But besides the costs, one of the factors which will make it harder for the technology to be widely adopted, is that it requires engineers, computer administrators and people in every aspect of the ICT security sector to rethink their approch to security and learn new ways to think about it.

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