|
November
11, 2002
Keeping
Information Secure With Noisy Light
EVANSTON,
Ill. — Put aside images of World War II espionage and codebreaking.
Today cryptography is vital to the security of a form of communication
and commerce never imagined 60 years ago: the Internet. Researchers
at Northwestern University now have demonstrated a new high-speed
quantum cryptography method that uses the properties of light to
encrypt information into a form of code that can only be cracked
by violating the physical laws of nature.
In
the open and global communication world of the Internet, information
security is a critical issue because conventional cryptographic
technologies cannot be relied upon for long-term security. Once
optimized, the Northwestern method could replace the mathematical
cryptography currently used by businesses, financial institutions
and the military for secure communication. The innovative protocol
promises security even against information security’s greatest
foe: the not-yet-invented but still-feared powerful quantum computer,
which could break almost any conventional code.
"As
computing power and data traffic grow and information speeds get
faster, cryptography is having a hard time keeping up," said
Prem Kumar, professor of electrical and computer engineering at
the McCormick School of Engineering and Applied Science and co-principal
investigator on the project. "New cryptographic methods are
needed to continue ensuring that the privacy and safety of each
person’s information is secure.
"Our
research team has succeeded in encrypting real information, sending
the message over a University fiber optics system at very high speeds,
and decrypting the information, which is no small feat. Other quantum
cryptography methods are slow and impractical for long-distance
or high-speed communication, whereas ours shows great potential
for real-world applications."
The
researchers transmitted encrypted data at the rate of 250 megabits
per second. Because it uses standard lasers, detectors and other
existing optical technology to transmit large bundles of photons,
the Northwestern protocol is more than 1,000 times faster than its
main competitor, a technique based on single photons that is difficult
and expensive to implement.
"No
one else is doing encryption at these high speeds," said Kumar,
who has a secondary appointment in the department of physics and
astronomy at the Judd A. and Marjorie Weinberg College of Arts and
Sciences.
The
Northwestern method, which is geared toward securing the public
fiber optic infrastructure, uses a form of "secret key"
cryptography. In this type of cryptography, the two people communicating,
say Alice and Bob, have the same secret key. If Alice wants to send
a secure message to Bob, she sends a message in a "locked box,"
which Bob can open.
In
the case of the Northwestern method, to encode her message Alice
uses the key to manipulate the light, creating a pattern more complex
than just "on" or "off." The method takes advantage
of the granularity of light, known as quantum noise, which is integrated
with the secret key’s pattern. (Random polarization is one
way to change the light’s granularity.) To someone without
the key, say the eavesdropper Eve, the information is indecipherable
— the stolen message contains too much "noise." Bob,
with the secret key, has the pattern and can receive the signal
with much less noise, allowing him to read Alice’s encoded
message.
Having
demonstrated that their high-speed encryption protocol works on
a real network with real data, the researchers now are working toward
speeds of 2.5 gigabits per second, which is the rate at which regular
information is currently transmitted over the Internet’s fiber
optic network.
"Current
cryptographic schemes are vulnerable because as computers get more
powerful the cryptography gets slower due to longer and longer keys,"
said Horace Yuen, professor of electrical and computer engineering
with a secondary appointment in physics and astronomy. He is principal
investigator and theorist on the cryptography project.
"What
we offer is a quantum cryptography system that is unconditionally
secure, fast, easy to manage and cost-efficient. Our technology
promises a realistic security solution to increasing computing power.
We expect to develop a practical application within five years."
The
Northwestern research team is working with two industrial partners,
Telcordia Technologies of Red Bank, N.J., and BBN Technologies of
Cambridge, Mass., to develop prototype systems for integration into
the core optical networks of the Internet.
Northwestern
has filed a number of patents based on the technology developed
at the University.
The
quantum cryptographic research project is supported by a five-year,
$4.7 million grant from the Defense Advanced Research Projects Agency
(DARPA). The communication protocol that is the backbone of today’s
Internet came out of a computer networking system begun by DARPA
in the 1960s.
|