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BBN Technologies, which is working with Northwestern to develop commercial quantum cryptography prototype systems for optical-fiber networks running over the Internet. Several start-ups have also cropped up, including Swiss company 10 Id Quantique and New York-based 11 Magiq Technologies, each promising to deliver commercial quantum cryptography technology sometime in 2003. How it works The Northwestern technique uses a form of "secret key" cryptography. In this scenario, the two people communicating with each other--say Alice and Bob--use the same secret key. Alice sends Bob the key with which he can decipher the message. This differs from the "public key" encryption system in which typically, both Alice and Bob will have a private key that they keep secret, and a public key that they publish. An encrypted message sent by Alice to Bob using the public key can be decrypted by the private key, and vice versa. Applying the Northwestern method to encode her message, Alice would use the key to manipulate light, creating a pattern more complex than the traditional way of transmitting data in terms of zeros and ones. Different combinations and strings of zeros and ones are used to represent information. The Northwestern technique takes advantage of the granularity of light, known as quantum noise, which is revealed only through the secret key's pattern. One method the team used to change the light's granularity was randomly polarizing the light. To Eve, the eavesdropper, who does not have the key, the data is indecipherable because the lifted message emits too much fuzz. Bob, however, who has the secret key, can get the pattern and can receive the signal with much less disturbance. Today, mathematical encryption that relies on schemes such as the RSA algorithm are considered secure because cracking the keys used to encrypt data is likely to take many years. The RSA algorithm is the most widely used Internet communications encryption program. The larger the prime numbers used to make keys, the longer it would take to crack the encryption. It relies on the assumption that when prime numbers--those divisible only by themselves and the number one--are very long, they are extremely difficult to generate and determine. Distributed computing involves spreading computing tasks across hundreds of thousands of computers--on the Internet or in private networks--that would otherwise be sitting idle. This technique has been used to overcome several mathematical challenges. One group last year found the 13 largest prime number, while another group deciphered a 14 message encoded with RSA Security's RC5-64 encryption algorithm. In years ahead, as computers become more powerful--perhaps through the advent of 15 quantum computing, which can carry out multiple calculations simultaneously--these systems might crack the stashed-away code. Kumar said that his team at Northwestern is working with two partners, Telcordia Technologies and BBN Technologies, to try to put the technology to commercial use. The university has filed a number of patents based on the research. This would amplify the stream of photons, letting them travel a greater distance undisturbed. If successful, quantum cryptography would be able to move beyond the constraints of a dedicated fiber-optic line between two points and extend out to wider networks like the Internet.
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