Researchers One Step Closer to Wide-Scale Use of Quantum Encryption Techniques

Latest progress in the field of quantum computers might shortly allow hackers access to machines that are adequately powerful to break even the most difficult standard Internet security codes. If the codes cracked, then the entire online data, such as bank transactions and medical records, can be unprotected and come under attack.

Razvan Dan Paun/

In order to overcome this potential threat, scientists are making use of the same strange characteristics that steer quantum computers to develop theoretically hack-proof types of quantum data encryption.

At present, an innovative system created by researchers from Duke University, The Ohio State University, as well as Oak Ridge National Laboratory can enable the use of such quantum encryption techniques to get us a step nearer to large-scale use. The system has the potential to develop and distribute encryption codes at the rates of megabits per second — nearly 5-10 times faster than prevalent techniques and equivalent to existing Internet speeds while operating multiple systems at the same time.

The team has shown that the method is immune to common attacks, even when equipment defects occur that might lead to leaks.

We are now likely to have a functioning quantum computer that might be able to start breaking the existing cryptographic codes in the near future. We really need to be thinking hard now of different techniques that we could use for trying to secure the internet.

Daniel Gauthier, Professor of Physics, The Ohio State University

The outcomes of the study have been published in the online edition of the Science Advances journal on November 24th, 2017.

When a hacker looks at our bank transactions, online purchases, and medical records, they seem to be like gibberish to them. This is because of ciphers known as encryption keys. When personal information is transferred through the web, it is initially disintegrated by means of one such key, and it is then put together by the receiver with the same key.

If this system has to be operative, then both parties should have access to the same key. Moreover, the key has to be held confidential. Quantum key distribution, or QKD, puts to good use one of the basic characteristics of quantum mechanics — evaluating tiny bits of matter such as photons or electrons eventually alters their characteristics — to swap the keys such that both parties are instantly notified about a potential breach of security.

Despite the fact that QKD was initially theorized in the year 1984 and put to effect soon after that, the technologies to assist in large-scale application of QKD have only now been emerging online. At present, European companies are selling laser-based systems for QKD, and last summer, in a largely advertized event, China used a satellite to transfer a quantum key to two land-based stations positioned 1200 km from each other.

According to Nurul Taimur Islam, a graduate student in physics at Duke University, the difficulty faced while using majority of these systems is that they send keys only at comparatively low rates (i.e. from tens to hundreds of kilobits per second), a speed very slow for much of the practical applications on the Internet.

At these rates, quantum-secure encryption systems cannot support some basic daily tasks, such as hosting an encrypted telephone call or video streaming.

Nurul Taimur Islam, Graduate Student in Physics, Duke University

Similar to various QKD systems, the key transmitter developed by Islam uses a weakened laser for encoding information on discrete light photons. However, they discovered a method for packing still more information onto individual photons, rendering their method considerably faster.

Their system achieves the encoding of two bits of information onto a single photon in the place of one by modifying the time of release of the photon as well as its characteristic known as the phase. This knack coupled with high-speed detectors designed by Clinton Cahall, a graduate student in electrical and computer engineering, and Jungsang Kim, professor of electrical and computer engineering at Duke University, enhances the ability of their system to send keys 5-10 times faster than other techniques.

It was changing these additional properties of the photon that allowed us to almost double the secure key rate that we were able to obtain if we hadn’t done that,” stated Gauthier, who was earlier a professor of physics at Duke, and has now joined OSU.

The QKD will be ideally secure in an ideal sphere. An endeavor to hack a key transfer will leave behind errors on the transmission, which can be easily zeroed in on by the receiver. However, real-time use of QKD mandates the use of faulty equipment, and such faults can open up leaks, which hackers can use to their advantage.

The team cautiously identified the restrictions posed by each equipment piece used by them. Subsequently, they collaborated with Charles Lim, professor of electrical and computer engineering at the National University of Singapore at present, to include these experimental defects into the theory.

We wanted to identify every experimental flaw in the system, and include these flaws in the theory so that we could ensure our system is secure and there is no potential side-channel attack.

Nurul Taimur Islam

Despite the fact that the transmitter developed by the team mandates certain special parts, all the components are commercially accessible at present. Encryption keys encoded onto light photons can be transferred through prevalent optical fiber lines buried under cities, rendering it comparatively uncomplicated to include their transmitter and receiver into existing Internet infrastructure.

All of this equipment, apart from the single-photon detectors, exist in the telecommunications industry, and with some engineering we could probably fit the entire transmitter and receiver in a box as big as a computer CPU,” explained Islam.

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