Quantum cryptography could be used to provide totally
secure video conferences, according to Toshiba's Cambridge Research
Laboratory, which demonstrated its technology at the recent
business-focused showcase hosted by the Department of Trade &
Industry.
Toshiba Cambridge said quantum cryptography allows users on an
optical fibre network to refresh their encryption keys frequently
in a completely secret way. It takes advantage of the nature of
light, sending encoded single photons ("particles" of light) along
standard telecom fibres.
In addition to frequent key generation, the benefit of quantum
cryptography is that any attempt to break the cryptographic key by
tapping into a stream of data can be detected.
Andrew Shields, group leader in research and development for
quantum cryptography at Toshiba Cambridge, said the quantum
approach allows cryptographic keys to be distributed securely.
These are required to unscramble the encrypted message. Other
approaches to encryption, such as public key infrastructure, rely
on a key that is computationally difficult to crack. "Quantum is
fundamentally secure," he said.
The security of quantum cryptography derives from quantum
mechanics, which was devised in the early part of the 20th century
and is widely used to describe processes and phenomena such as the
energy level of atoms.
According to Toshiba Cambridge, the basis for quantum cryptography
is that, in general, measurement alters the state of an unknown
single quantum. This is why it is impossible for a third party to
duplicate a key formed by quantum cryptography.
At the DTI, Toshiba Cambridge was able to show that a cryptographic
key could be transmitted securely over a fibre optic cable.
The approach relies on transmitting a single photon of light to
represent each binary one or zero bit in an encryption key. Because
each bit is carried by a single photon, it is not possible for a
hacker to tap in and remove part of the signal, Toshiba Cambridge
said.
This is because a single photon cannot be split, so if a hacker
measures the photons on the fibre, they will not reach the intended
recipient. Only the photons that arrive at the recipient are used
to form the key, so the hacker cannot gain any useful information
by a "tapping" attack.
The benefit of using optical fibre is that the key can be readily
changed. In the demonstration at the DTI, Toshiba Cambridge showed
how each frame of video in a video conference could be secured with
a new key.
"We can generate up to 100 keys per second," said Shields. This
means there is no risk arising from a stored key being discovered
by a would-be attacker. "It would take an enormous computational
resource to crack this frame by frame," Shields added.
