On Sept. 4, researchers at Toshiba’s European research laboratory in Cambridge, England announced that they have discovered a way to improve security on computer networks by means of a new encryption technique.
The method, known as quantum key distribution (QKD), has previously been available only on a point-to-point basis within an optical network. The research team was able to expand the method to accommodate up to 64 users on a single photon detector by means of a “quantum access network,” which will significantly reduce the amount of hardware needed for each user to use QKD. This was done by figuring out how to distinguish each user's stream of photons from that of each other user.
The data bitrate of such advanced encryption is currently very low at the 64-user level. The team had to lower the number of users to eight just to get a rate of 0.25 Mbps. But as the research paper says, “continuous operation over a month would allow unconditionally secure one-time pad encryption of more than 10 GB of data for each user, which is enough for example to protect over 100,000 emails.”
QKD does not prevent surveillance of communications, but it does alert users to the fact that they are being spied upon. QKD works by encoding cryptographic keys in photons that are specially polarized. Because the act of observing a quantum system alters the system being observed, the polarization of photons observed by a third party, such as a government spying agency, will be altered, thus alerting the parties of a secret communication to the presence of a spy.
“One of the attractive things about quantum cryptography is that security comes in the form of the laws of nature,” said Andrew J. Shields, who co-authored the study and is the assistant managing director for Toshiba Research Europe. “It should, in principle, be secure forever.”
Current methods of cryptography typically rely on a cryptographic hash function, which provides security through a hexadecimal string that requires vast computing resources to hack. Unlike QKD on optical networks, cryptographic hash functions on photo-electronic connections do not alert users to spying efforts.
It is not yet known whether Toshiba will try to commercialize the research work of Dr. Shields' group. He said that the next objectives are to extend the range of the system further and use it in a live computer network.