BT bolsters research in quantum technologies
Friday, May 5, 2017 at 7:25AM
Roy Rubenstein in Andrew Lord, BT, Telecom Infra Project, post quantum, public key, quantum, quantum computing, quantum cryptography, quantum key distribution, quantum resistant, quantum safe algorithms, symmetric key

BT is increasing its investment in quantum technologies. “We have a whole team of people doing quantum and it is growing really fast,” says Andrew Lord, head of optical communications at BT.

The UK incumbent is working with companies such as Huawei, ADVA Optical Networking and ID Quantique on quantum cryptography, used for secure point-to-point communications. And in February, BT joined the Telecom Infra Project (TIP), and will work with Facebook and other TIP members at BT Labs in Adastral Park and at London’s Tech City. Quantum computing is one early project.

Andrew LordThe topics of quantum computing and data security are linked. The advent of quantum computers promises the break the encryption schemes securing data today, while developments in quantum cryptography coupled with advances in mathematics promise new schemes resilient to the quantum computer threat.    


Securing data transmission

To create a secure link between locations, special digital keys are used to scramble data. Two common data encryption schemes are used, based on symmetric and asymmetric keys. 

A common asymmetric key scheme is public key cryptography which uses a public and private key pair that are uniquely related. The public key is published along with its user’s name. Any party wanting to send data securely to the user looks up their public key and uses it to scramble the data. Only the user, which has the associated private key, can unscramble the data. A widely used public-key crypto-system is the RSA algorithm.


There are algorithms that can be run on quantum computers that can crack RSA. Public key crypto has a big question mark over it in the future and anything using public key crypto now also has a question mark over it.


In contrast, symmetric schemes use the same key at both link ends, to lock and unlock the data. A well-known symmetric key algorithm is the Advanced Encryption Standard which uses keys up to 256-bits long (AES-256); the more bits, the more secure the encryption.

The issue with a symmetrical key scheme, however, is getting the key to the recipient without it being compromised. One way is to deliver the secret key using a security guard handcuffed to a case. An approach more befitting the digital age is to send the secret key over a secure link, and here, public key cryptography can be used. In effect, an asymmetric key is used to encrypt the symmetric key for transmission to the destination prior to secure communication.

But what worries governments, enterprises and the financial community is the advent of quantum computing and the risk it poses to cracking public key algorithms which are the predominant way data is secured. Quantum computers are not yet available but government agencies and companies such as Intel, Microsoft and Google are investing in their development and are making progress.

Michele Mosca estimates that there is a 50 percent chance that a quantum computer will exist by 2030. Professor Mosca, co-founder of the Institute for Quantum Computing at the University of Waterloo, Canada and of the security firm, evolutionQ, has a background in cyber security and has researched quantum computing for 20 years.

This is a big deal, says BT’s Lord. “There are algorithms that can be run on quantum computers that can crack RSA,” he says. “Public key crypto has a big question mark over it in the future and anything using public key crypto now also has a question mark over it.”

A one-in-two chance by 2030 suggests companies have time to prepare but that is not the case. Companies need to keep data confidential for a number of years. This means that they need to protect data to the threat of quantum computers at least as many years in advance since cyber-criminals could intercept and cache the data and wait for the advent of quantum computers to crack the coded data.   


Upping the game

The need to have secure systems in place years in advance of quantum computer systems is leading security experts and researchers to pursue two approaches to data security. One uses maths while the other is based on quantum physics.

Maths promises new algorithms that are not vulnerable to quantum computing. These are known as post-quantum or quantum-resistant techniques. Several approaches are being researched including lattice-based, coding-based and hash-function-based techniques. But these will take several years to develop. Moreover, such algorithms are deemed secure because they are based on sound maths that is resilient to algorithms run on quantum computers. But equally, they are secure because techniques to break them have not been widely investigated, by researchers and cyber criminals alike.   

The second, physics approach uses quantum mechanics for key distribution across an optical link, which is inherently secure.  

“Do you pin your hopes on a physics theory [quantum mechanics] that has been around for 100 years or do you base it on maths?” says BT’s Lord. “Or do you do both?”


In the world of the very small, things are linked, even though they are not next to each other


Quantum cryptography 

One way to create a secure link is to send the information encoded on photons - particles of light. Here, each photon carries a single bit of the key.

If the adversary steals the photon, it is not received and, equally, they are taking information that is no use to them, says Lord. A more sophisticated technique is to measure the photon while it passes through but here they come up against the quantum mechanical effect where measuring a photon changes its parameters. The transmitter and receiver typically reserve at random a small number of the key’s photons to detect a potential eavesdropper. If the receiver detects photons that were not sent, the change alerts them that the link has been compromised.

The issue with such quantum key distribution techniques is that the distances a single photon can be sent are limited to a few tens of kilometres only. If longer links are needed, intermediate secure trusted sites are used to regenerate the key. These trusted sites need to be secure.

Entanglement, whereby two photons are created such that they are linked even if they are physically in separate locations, is one way researchers are looking to extend the distance keys can be distributed. With such entangled photons, any change or measurement of one instantly affects the twin photon. “In the world of the very small, things are linked, even though they are not next to each other,” says Lord.

Entanglement could be used by quantum repeaters to increase the length possible for key distribution not least for satellites, says Lord: “A lot of work is going on how to put quantum key distribution on orbiting satellites using entanglement.”

But quantum key distribution only solves a particular class of problem such as protecting data sent across links, backing up data between a bank and a data centre, for example. The technique is also dependent on light and thus is not as widely applicable as post-quantum algorithms. "There is a view emerging in the industry that you throw both of these techniques [post quantum algorithms and quantum key distribution] especially at data streams you want to keep secure."



BT working with Toshiba and optical transport equipment maker ADVA Optical Networking have already demonstrated a quantum protected link operating at 100 gigabits-per-second.

BT’s Lord says that while quantum cryptography has been a relatively dormant topic for the last decade, this is now changing. “There are lots of investment around the world and in the UK, with millions poured in by the government,” he says. BT is also encouraged that there are more companies entering the market including Huawei.

“What is missing is still a little bit more industrialisation,” says Lord. “Quantum physics is pretty sound but we still need to check that the way this is implemented, there are no ways of breaching it; to be honest we haven't really done that yet.”

BT says it has spent the last few months talking to financial institutions and claims there is much interest, especially with quantum computing getting much closer to commercialisation. “That is going to force people to make some decisions in the coming years,” says Lord. 

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