Associate Professor Sarah Johnson performs research in the fields of signal processing, error correction coding and information theory.

A Key to a Secure Future

In a digital age where information privacy is key, University of Newcastle Associate Professor Sarah Johnson is cracking the code on keeping business, government, defence and your secrets secure.

Associate Professor Sarah Johnson with mathematical equations A/Prof Johnson is an expert on error correction codes which improve the reliability and quality of digital technologies such as television, DVD players, mobile phones and the Internet.

In partnership with Quintessence Labs and researchers at the Australian National University, A/Prof Johnson is developing next generation quantum key distribution (QKD) technology that will enable two parties to produce a random shared key known only to them. The key can then be used to encrypt and decrypt messages to guarantee secure transmission of data.

Information like email, network security, e-commerce, credit-card, security numbers and sensitive company documents are some of the applications QKD could be used for, according to A/Prof Johnson.

"Banks, government, defence forces and the corporate world are just some of the areas set to benefit from the information protection solutions we are designing," A/Prof Johnson said.

"Technology is a major part of today's critical infrastructure from health to power to e-commerce. Data security is of the utmost importance, whether it's a company protecting itself from espionage attacks or a country guarding against cyber-terrorism," she said.

One of the greatest challenges of cryptography is ensuring that a third party does not get access to the secret key and therefore confidential information. Specialising in iterative error-correcting coding, A/Prof Johnson role is to ensure that the transfer of the key is clear, reliable and secure.

A fundamental aspect of digital communications, error-correction coding uses complex mathematical algorithms to eliminate 'noise' or errors during transmission – such as interference from storms or competing digital devices.

Current methods for secure communications are in danger of becoming cracked in the future by quantum computers that can factor large numbers, which is why QKD technology is gaining so much attention, as the Australian Research Council (ARC) Future Fellow explains.

"In the case of quantum cryptography, we're not just using error-correction coding to clean up 'noise', we're using it to detect interference and the presence of any third party 'listening in'," she said.

"The very nature of a quantum mechanical system means that if anyone even observes or listens in on the quantum channel, it alters the state of the photons and thus the message, alerting the users to interference.

Quantum cryptographic systems can be used in optical fibre networks, wireless point to point, satellite uploads. As Australia moves toward a National Broadband Network (NBN), technologies like QKD will become increasingly important.

"QKD technology is the way of the future and has already been used to protect bank transfers, ballot results and computer networks in Europe. For example, Geneva residents used quantum cryptography to transmit their voting results for the 2007 parliamentary elections.

"It has been quite expensive to use QKD, but the new type of continuous variable QKD we are investigating uses standard telecommunications-type receivers rather than single photon detectors making it significantly cheaper to produce."

The QKD technology is part of a $300,000 ARC Linkage Grant with an expected product date by 2016.

"With technology expanding so rapidly, there is a growing need for better and faster error correction," said A/Prof. Johnson, "Ultimately, new error correction codes can be incorporated into the next generation of communications equipment and we're currently studying best case scenarios for networks where multiple users can use a system together securely."  

Johnson authored a book in 2010 titled Iterative Error Correction, which discusses the theory, design and implementation of powerful coding techniques known as turbo, low-density parity-check and repeat-accumulate codes. 

Based at the University of Newcastle's Centre for Complex Dynamic Systems and Control and the Signal Processing and Microelectronics Group, A/Prof Johnson is also working on improving digital communication, like mobiles and wi-fi networks, through her specialty in iterative error correction coding.  

In addition to her error-correction coding work, A/Prof Johnson has been collaborating with leading neuroscientists at the University of Newcastle over the past 18 months through her work with the Priority Research Centre for Bioinformatics, Biomarker Discovery and Information-Based Medicine

Creating solutions using mathematical algorithms across three different projects, A/Prof Johnson is aiming to improve current medical image processing, create a new imaging device and, ultimately, make steps towards a virtual reality system for medical research.

"Working towards improving the imaging and building a new imaging device is an interesting project because it involves quite a lot of different technological areas and collaborating with colleagues in computer science, electrical engineering and biomedical science."

Whether it is protecting or unveiling information, A/Prof Johnson is helping deliver the keys to a clearer image of the future.