Worldwide we are all becoming increasingly reliant on the security of information and communications. At the same time, current methods used for security are becoming ever more vulnerable. It is known that encryption techniques widely used today can be broken by a large and powerful quantum computer, when this gets built in the – perhaps not too distant – future. For information that is only required to be secure for a short time now, this threat is clearly just looming. However, for sensitive information that requires a long security “shelf-life”, the threat is already here. Encrypted communications can be stored now and broken in the future, when the tools exist. Clearly new approaches to security are required.
In general, secure communications are achieved by the sender (usually called “Alice”) encrypting her message, so it cannot be read by anyone who intercepts it and for whom it is not intended (usually called “Eve” – the eavesdropper). At the intended receiver (usually called “Bob”) end, the message has to be decrypted, so it can be read. Encryption and decryption methods are needed that are not vulnerable to quantum computer attack. One approach is to utilise shared keys – for encryption and decryption – and cryptographic techniques (that consume these keys) which are immune to such attacks. Then the security of the message transmission is determined by the security of the key distribution mechanism. This is where the quantum technology comes in – it provides a secure method of quantum key distribution, or QKD.
Quantum mechanics dictates that when any of us try to measure or interact with a quantum system to learn about what it is doing, we inevitably and irreversibly disturb it. This relationship between disturbance and information gained is fundamental. It is not something that can be overcome by building better measurement devices and probes in the future – it is built into Nature. Taken into the context of communications scenarios, it simply means that where the distribution of encryption keys for securing sensitive messages is implemented with quantum light signals, anyone covertly attempting to gain information about the keys will necessarily disturb some of the light signals as they do so. Thus, Nature ensures that eavesdroppers cannot avoid being detected – in fact even if they try to use other quantum technologies to examine the light signals.
Quantum secure communication systems use these quantum effects to distribute encryption keys with quantum light signals. These keys are then utilised to secure all manner of sensitive data transmissions, such as bank transactions or personal health records.
The Quantum Communications Hub is working on developing and commercialising quantum secure communications technologies and services with applications that will revolutionise communications across multiple sectors.