CAMBRIDGE, England, Dec. 14 -- Toshiba Research Europe Ltd. in Cambridge has demonstrated a "robust and user-friendly" way to use quantum cryptography to detect unauthorized eavesdropping and to distribute secret keys on optical fiber networks. It said the first beneficiaries are likely to be banks and other large corporations with sensitive information. Toshiba and MCI recently conducted a trial of the system on installed telecommunications fiber in which they demonstrated the ability to send secret keys for an entirely automated and uninterrupted session of nearly a week. Previous attempts lasted only minutes and required continual adjustment. Toshiba said its system, which also holds the distance record for complete key transfer, serves keys at a rate of up to 100 per second and provides an absolute guarantee of the secrecy of each one. The first application of quantum cryptography is to distribute secret keys. These keys, long strings of zeros and ones, are the basis of secure communications and transactions in computer networks. For the security of such systems, it is important that the keys not only remain secret, but also that they are regularly refreshed. The security of quantum cryptography relies on the ability to encode the bit material for the secret keys on individual photons sent along the fiber. However, these quantum bits are extremely sensitive to fluctuations in the transmission apparatus, such as temperature changes, or even tiny movements of the fiber. Toshiba said its system has eliminated these problems by introducing a technique that preserves quantum information over long propagation distances. This allows the quantum cryptography system to be self-initiating and to operate continually, 24 hours a day, 7 days a week, without any human management. "Uniquely quantum cryptography provides a way to distribute keys in a manner that is fundamentally secure and therefore independent of future developments in computing and code breaking. The technique is not only future proof, but also provides a convenient method for key distribution and management that allows companies and organizations to build self-reliant secure networks," Toshiba said. For more information, visit: www.toshiba-europe.com