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Sci Tech
Using light for encryption
TODAY CRYPTOGRAPHY is vital to the security of the Internet. Researchers at Northwestern University have now 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.
Once optimised, the Northwestern method could replace the mathematical cryptography now used for secure communication.
The innovative protocol promises security even against information security's greatest foe: the quantum computer, which could break almost any conventional code, according to the university's press release.
"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. New cryptographic methods are needed to continue ensuring that the privacy and safety of each person's information is secure.
The team has succeeded in encrypting real information, sending the message over a University fibre optics system at very high speeds, and decrypting the information, say the researchers. Other quantum cryptography methods are slow and impractical for long-distance or high-speed communication. In the new method the researchers transmitted encrypted data at the rate of 250 megabits per second. The Northwestern method uses a form of `secret key' cryptography. Here, 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 new 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. 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.
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