What is quantum cryptography?
Quantum cryptography, also called quantum encryption, applies principles of quantum mechanics to encrypt messages in a way that it is never read by anyone outside of the intended recipient. It takes advantage of quantum’s multiple states, coupled with its "no change theory," which means it cannot be unknowingly interrupted.
Performing these tasks requires a quantum computer, which have the immense computing power to encrypt and decrypt data. A quantum computer could quickly crack current public-key cryptography.
Why quantum cryptography is important:-
Companies and governments around the world are in a quantum arms race, the race to build the first usable quantum computer. The technology promises to make some kinds of computing problems much, much easier to solve than with today’s classical computers.
One of those problems is breaking certain types of encryption, particularly the methods used in today’s public key infrastructure (PKI), which underlies practically all of today’s online communications. “I’m certainly scared of what can be the result of quantum computing,” says Michael Morris, CEO at Topcoder, a global network of 1.4 million developers. Topcoder is part of Wipro, a global consulting organization. It’s also working on finding solutions to quantum computing programming challenges.
“Instead of solving one problem at a time, with quantum computing we can solve thousands of problems at the same processing speed, with the same processing power,” Morris says. “Things that would take hundreds of days today could take just hours on a quantum computer.”
The commercial quantum computers available today are still far from being able to do that. “The theories have advanced farther than the hardware,” says William Hurley, IEEE senior member, founder and CEO of Austin-based quantum computing company Strangeworks. “However, we shouldn’t wait for the hardware to motivate the switch to post-quantum cryptography.”
Who knows what kind of technology isn’t available on the public market, or is operated in secret by foreign governments? “My fear is that we won’t know that the quantum computer capable of doing this even exists until it’s done,” says Topcoder’s Morris. “My fear is that it happens before we know it’s there.”
Quantum key distribution is unhackable:-
This is where the laws of quantum physics can come to the rescue. Quantum key distribution (QKD) is a method of sending encryption keys using some very peculiar behaviors of subatomic particles that is, in theory at least, completely unhackable. The land-based version of QKD is a system where photons are sent one at a time through a fiberoptic line. If anyone is eavesdropping, then, according to the principles of quantum physics, the polarization of the photons is affected, and the recipient can tell that the message isn’t secure.
China is furthest ahead with QKD, with dedicated pipes connecting Beijing, Shanghai, and other cities. There are also networks in Europe. In the United States, the first commercial QKD network went live this past fall. The Quantum Xchange, connecting New York City’s financial firms with its data centers in New Jersey, rents space on existing fiberoptic networks, then uses its own QKD senders and receivers to send the secure messages on behalf of clients. The company plans to expand to Boston and Washington, D.C. later in 2019.
However, the technology is extremely slow and requires expensive equipment to send and receive the individual photons. According to John Prisco, CEO and president of Quantum Xchange, a customer would need to buy a transmitter and a receiver, each of which costs in the neighborhood of $100,000. “It’s not too terribly different from other high-speed fiber optics communication equipment,” he says. “And the price will come down over time as more companies provide the hardware.”
The big breakthrough last year was that QKD systems no longer require special pipes, says Woodward. “Now it looks like they’ll be able to use existing fiber networks, so they don’t have to lay new fiber.”
Then there’s the satellite-based approach. This one uses the principle of entanglement, which Einstein called “spooky action at a distance” and refused to believe was real. Turns out, it is real, and China has had a quantum communication satellite up and working for a couple of years now.
Entanglement isn’t about instantaneous communications that break the speed of light speed limit, says Woodward. The way that it works is that two particles become entangled so that they have the same state, and then one of these particles is sent to someone else. When the recipient looks at the particle, it’s guaranteed to be the same state as its twin.
If one of those particles changes, it doesn’t mean that the other particle instantly changes to match — it’s not a communication system. Plus, the state of the two entangled particles, while identical, is also random. “So, you can’t send a message,” says Woodward, “but you can send an encryption key, because what you really want in a key is a sequence of random digits.”
Now that the sender and the receiver both have the same random key, they can then use it to send messages using symmetric encryption over traditional channels. “China has leapfrogged everyone with this satellite,” says Woodward. “Everyone said it couldn’t be done, that passing through the atmosphere would drop it out of superposition, but the Chinese have been able to do it.” To receive the signals, companies would need to put something that looks like a telescope on their rooftops, he says, and then install some processing equipment.
Neither ground-based nor satellite-based quantum key distribution is practical for general use since both require very specialized and expensive equipment. It could, however, be useful for securing the most critical and sensitive communications.
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