"It’s related to national/supranational sovereignty, which is of utmost importance in the current context”
A little mysterious, sometimes confusing, quantum technologies are at the heart of many inventions that we use every day. Equally promising are quantum communications, and their application to the security of data exchange.
Since two years, Orange has been involved in three European collaborative actions dealing with quantum communications: the CiViQ (Continuous Variable Quantum communications) project, the OPENQKD (Open European Quantum Key distribution testbed) project and the QOSAC (Quantum Overarching System Architecture Concepts) research contract.
Quantum Physics: from everyday life applications to network security
The word “quantum” relates to the world of the infinitely small, therefore the constituent elements of matter (molecules, atoms, particles, etc.). The objects around us respect the laws of classical physics for space and time: for example, if a car is traveling from point A to point B at a certain speed, its arrival time at point B can be predicted according to its departure time from point A. When we consider the particles of matter constituting the objects of the universe (for example the atoms of the body of the car) this is no longer true. We must use the laws of quantum physics (which are different) to describe the behavior of the electrons of these atoms. For example, you cannot precisely define the speed and position of an electron, but only probabilistically. This is explained by the Heisenberg uncertainty principle. In summary, on the infinitely small scale, the characteristic variables (position, speed, etc.) are no longer deterministic but statistical.
The applications of quantum physics have been visible in our daily lives since the middle of the last century. First, there was the invention of electronic components such as transistors, followed in the 1960s by lasers. MRI (Magnetic Resonance Imaging), the electronic components in our everyday objects (such as mobile phones), CD-DVD players… all derive from research in the quantum field.
And there is a lot of excitement in research on these subjects. Research programs are launched all over the world and billions of euros are invested. This concerns the development of high performance computers, increasingly precise and efficient sensors and measuring devices. Likewise, research is taking place in the field of quantum communications for the security of communications networks.
In 2018, the European Commission (EC) launched a major research program of €1 billion over 10 years: the Quantum Flagship[i]. Several projects[ii] have been launched, including the CiViQ project (Continuous Variable Quantum communications) in which Orange is working with very skilled quantum communications actors. The goal is to define quantum cryptography solutions allowing to transmit ultra secure information.
In addition, in 2019 the EC launched another call for projects aimed at building an infrastructure for testing and evaluating quantum cryptography solutions across Europe. In this context Orange is participating in the OPENQKD (Open European Quantum Key distribution testbed) project with 37 other partners.
Finally, the EC has also launched a program called EuroQCI (Quantum Communication Infrastructure): it’s an initiative launched by several countries. France has joined this initiative at the end of 2019[iii]. The ambition is to provide Europe with a quantum communications infrastructure for both terrestrial and space. In this context, Orange is involved in the QOSAC (Quantum Overarching System Architecture Concepts) research contract whose main objective is to work on quantum communications for the networks security and on the interfaces between spatial and terrestrial segments.
Quantum cryptography: a solution to deal with the threat of high performance computing
The computing capacity of computers has been multiplied by 80 over the last 10 years[iv]: the most powerful computer has a capacity of 148 Petaflops (FLOPS = FLoating point Operations Per Second) (or 148 million billion operations per second). France has recently bought a supercomputer (called “Jean Zay”)[v]: the machine, at full power, offers a computing capacity equivalent to the one of 40,000 personal computers (16 Petaflops, or 16 million billion operations per second), doubling France’s computing power in research. The arrival of quantum computers should further increase the available computing capacities. They could thus weaken the cryptographic solutions currently implemented to secure our data by breaking the current cryptography algorithms[vi].
Solutions to this problem are being developed, some of which are primitives (or cryptographic functionalities) to use quantum physics principles to carry encryption keys more securely. This technique is called QKD (Quantum Key Distribution), which means quantum distribution of encryption keys.
Orange researchers are studying these solutions in order to keep network security still as robust as ever against hacker attacks, even in the future. Indeed, we exchange a lot of sensitive data on networks that concern our bank accounts, our health and other information that must be kept confidential. We want this data to remain confidential for as long as possible (at least our whole life for health data for example): this is called long-term security. So we have to anticipate and prepare for the arrival of the quantum computers and their potential use to break cryptographic codes. This is why Orange is studying quantum communication/cryptography solutions.
QKD solutions use photons as the carrier of quantum information and are therefore based on optics. An encryption key is a (secret) code which is combined with the data of the messages to be transported. It makes it possible to keep these messages confidential. Indeed the data becomes unusable by someone who has not the deciphering key. It’s like a padlock, with a unique key, put on each exchanged message (see Figure 1). In the case of symmetric cryptography considered here, this (secret) key must be shared between the two ends of a link, that is to say between the two people (often called Alice and Bob) who must exchange data. The aim is to ensure the confidentiality and integrity (no changes on the content) of the exchanged data.
If we refer to Figure 1, we can identify three building blocks:
- a random number generator based on quantum principles called QRNG (Quantum Random Number Generator), which is used to create the secret key,
- the exchange of the key (for this, we use a transmitter (Tx with a laser and a modulator) and a receiver (Rx with photodiodes and signal processing devices)): it’s the QKD itself,
- a ciphering algorithm, the same as those used in classical cryptography: i.e. One Time Pad (OTP) (performing a XOR function with the data to be protected. It requires a continuous stream of encryption keys that are perfectly random and having the same length as the original information stream of the data to be transported) or else Advanced Encryption Standard (AES) (i.e. AES-128 or AES-256 with a key length of 128 or 256 bits that is regularly renewed to ensure the security of transmitted data).
Figure 1: Symmetric encryption with quantum devices.
We can describe the advantage of QKD for the exchange of encryption keys, compared to current solutions, with the following image. If we imagine that the exchange of the constituent bits of the secret key (continuation of “0” and “1”) between Alice and Bob is done by sending balls on which are written numbers (“0” or “1”), a spy can intercept the balls and obtain the key. Using quantum communications, it’s as if we were exchanging soap bubbles: if someone tries to catch them, they disappear which gives two advantages: it’s detected (Bob does not receive the bubbles) and a spy cannot discover our (secret) key as the bubbles are destroyed. In reality, the quantum information transmitted are qubits and which are here photons (quanta of light energy) transported, either in optical fibers, or in free space. All the photons’ interceptions change their characteristics irreversibly.
The advantage of quantum key exchange is that it can rapidly detect a spy/hacker who tries to steal the secret key during the exchange (Figure 2). We can then decide to update the encryption key and continue to guarantee the security of the transmitted information. A sufficient rhythm of key renewing is necessary to limit the risks.
Figure 2: What QKD can do to cope with high performance computer threat.
(Production: Fiona Giboire)
Implementation of this type of solutions to secure the exchange of ciphering keys: a number of limitations
There are several technological approaches to implement QKD, as examples we can mention:
- DV-QKD (Discrete Variable QKD) which uses single photon sources and receivers. The first, famous QKD protocol is the BB84 which uses polarization of light to code the secret key,
- CV-QKD (Continuous Variable QKD) which uses the quadrature (amplitude and phase) of the electromagnetic field (small pulses) to code the secret key as well as coherent detection, similar to the one used in WDM (Wavelength Division Multiplexing) transmission systems (Figure 3). The CV-QKD was proposed in 2002 by a French laboratory (F. Grosshans and P. Grangier[vii]).
In summary, the DV-QKD rather appeals to the corpuscular nature of light and the CV-QKD exploits its wave nature.
Figure 3: Optical laboratory dedicated to WDM transmissions – Orange Labs Lannion.
From an equipment point of view, the commercial solutions available are based on DV-QKD, which was the first implementation of QKD with a very important research work to build light sources able to generate single photons. However, there are prototypes of CV-QKD solution. Existing business proposals are currently very expensive. This is the reason why it’s important to work on reducing the cost and size of these solutions, which will notably involve photonic integration. Some start-ups have already developed QKD systems which should be available this year.
In addition, the reach of QKD systems using optical fiber is limited: from 60 to 80 km for commercial systems to a few hundred kilometers for some prototypes. However, quantum signals cannot be amplified by fiber amplifiers (for example EDFA: Erbium Doped Fiber Amplifier) that are used in the long haul optical telecommunication systems. Depending on the applications, ranges of several hundred or even thousands of kilometers are to be protected with these quantum keys. In this case, it’s necessary to use so-called “trusted” nodes in which the key is regenerated. Practically, these trusted nodes can be located inside the amplification sites along the link. A key is then used for each fiber section between each trusted node. Thus, by making an “Exclusive OR” (XOR) type operation between the different sections, end-to-end protection of the link is carried out. The other solution is to use satellite links with a transport of the key in free space.
The co-propagation of the quantum channel (see Figure 1) with the WDM channels transporting the data consists in using a single fiber to transport the two types of signals (which are all made up of photons). Since it does not require a dedicated fiber it’s economically interesting. Indeed, it allows adding the quantum channel, at a wavelength different from the WDM channels already deployed, on the existing infrastructures without additional investments other than the QKD equipment. Due to the very low power level of the quantum signal (photon by photon), DV-QKD is more difficult to implement with co-propagation than CV-QKD. However, it’s necessary to study the integration of QKD solutions from a reach and engineering point of view so as not to disturb the WDM signals transported in the fibers. Recent progress concerning co-propagation with DV and CV-QKD are presented in [viii].
Regarding QRNG, integrated solutions (footprint of a few mm2) are now commercially available and are starting to be deployed.
Even if major progress has been made over the past fifteen years, the large-scale implementation of QKD solutions to secure networks still requires significant research and development efforts. Europe, as well as the great world powers, are fully aware of the strategic importance of these activities. Actually, it’s related to national/supranational sovereignty, which is of utmost importance in the current context. This sovereignty concerns our needs in terms of new working methods, technical supremacy in order to protect our data exchanges over the long term, or independence in equipment supply necessary for their implementation.
The goal of Orange’s commitment in the CiViQ, OPENQKD and QOSAC projects is to understand and evaluate the QKD solutions in order to see to what extent they can meet the operator’s needs to maintain an optimum level of security for its customers, even in the future.
CiViQ[ix]: a Research and Innovation project (2018-2021)
With 21 industrial partners (telecommunications operators and manufacturers) and academics[x], the CiViQ project, which started in October 2018 for a period of 3 years, was selected during the 1st call for Quantum Flagship projects. CiViQ only focuses on CV-QKD solutions for applications in optical fiber networks.
The main objective of CiViQ is to make QKD a widely deployed technology to secure communications and data transmission. For this goal, developments of solutions based on discrete components are implemented. In addition, work on the integration of electronic and photonic components is underway in order to prepare the next generation of QKD solutions.
One of CiViQ’s goals is to make CV-QKD technology widely available for high security applications. Different use-cases for different types of applications (operators or customers) are being studied and have allowed to define the characteristics and performances of the QKD systems necessary for their implementation in operators’ networks.
An important objective is also the coexistence of QKD devices with currently deployed optical communications systems.During the CiViQ project, the validation of the ability of QKD devices to operate transparently within flexible and dynamic networks will be evaluated. For this, evaluation tests in the laboratory and in the field are (and will be) carried out during the project for the defined use-cases. Integration into existing network infrastructures must be compatible with the SDN (Software-Defined Networking) paradigm to allow flexible deployment of new capacities and new services in telecommunications networks.Orange’s first contribution to the CiViQ project was to propose use-cases. Experimental work using the optical transmission skills of the Lannion teams is also planned, as well as work relating to cryptography.Beyond technical performance, the results expected after 3 years are a price reduction of a factor of 5 to 10 compared to existing solutions. On the Quantum Flagship time scale (in about 8 years), the expected results are to have CV-QKD on chip with 100 times reduction in price and 10-50 times reduction in system volume. It’s a real challenge!
OPENQKD[xi]: European H2020 project (2019-2022)
OpenQKD is a project launched in October 2019 with the aim of studying and testing, through field trials, the various QKD solutions available in Europe. Several trials associated with different use-cases are (and will be) deployed in Europe. This is the first milestone towards the European Quantum Networks EuroQCI project. The 37 partners[xii] come from different backgrounds, both industrial (telecommunications operators and equipment manufacturers) and academic (laboratories, institutes).
All QKD technologies (DV and CV) are eligible for this project, both on fiber and satellite infrastructure. However, currently, the only commercially available solutions are based on the DV-QKD approach.
The Orange contribution will be based on use-case proposition and the proposal of a use-case with a governmental customer of Orange. This field trial will be shared in two steps: the first steps will be dedicated to the validation of the experimental solution on an R&D network and the second step on the deployment of the solution at the customer premises. The first step will be done on Orange fiber infrastructure in collaboration with a QKD equipment supplier and the second step will be done with Orange Business Services (OBS) and its customer. The first step could be set at the end of 2020/beginning of 2021 and the experiment with the customer would be at the end of 2021 and during 2022.
Two kinds of solutions could be evaluated in the frame of OPENQKD, a classical solution based on discrete optical components and a second one using integrated photonics. Ultimately, a service offer could be proposed by OBS to its customers, based on the experimental results.
QOSAC: Research contract in the frame of EuroQCI
European Commission (Digital Assembly) has decided in 2019 to establish within 10 years a pan-European secure quantum backbone with terrestrial and space segments. The long term goal is the so-called Quantum Internet. To achieve this goal, it’s first necessary to get structured inputs to support the next QCI steps and establish the budgets for 2021-2027. QKD as a cryptographic primitive to improve network security is a key point to investigate. Also Interfaces between the Space QCI and the Terrestrial QCI components have to be detailed.
Three service use-cases have been provided by the EC:
1) Inter and Intra EU government communication
2) Inter Data Centers communication and
3) Critical infrastructure communication.
QOSAC is attached to a competitive study contract; the list of Orange partners cannot be published. Partners are taking into account the different network segments i.e. the space segment, the ground to space segment, and the terrestrial network, and are studying the user requirements, the global architecture, the performances and the upgradability. Foreseen impacts in terms of regulation are also considered. The project has begun at the beginning of this year and is planned to be finished at the end of 2020.
It’s important to note that these solutions will complement the powerful cryptography solutions currently implemented in Orange networks.Thanks to quantum communications we will be able to offer long term robust solutions to guarantee the security of the data. In order to complexify the hackers’ task, the keys will have to be changed regularly.Many different skills are needed to work on this subject: in the CiViQ and OPENQKD projects, we have pooled the talents of researchers in different fields such as optics, security and cryptography based in Lannion, Rennes, Caen and Paris. The same applies for QOSAC, with people with skills in telecommunications regulation as well.Furthermore, following the French “Quantum”[xiii] report at the request of the Prime Minister on January 9, 2020 by Paula Forteza, France should soon launch research programs on the subject of quantum communications because one of the ambitions displayed is to “Maintain a strategic independence in cryptography technologies”. There is no doubt that Orange will contribute too.
"It’s related to national/supranational sovereignty, which is of utmost importance in the current context”
The authors thank Nicolas Brochier for his valuable comments and suggestions.
[vii] “Continuous variable quantum cryptography using coherent states”, F Grosshans, P Grangier – Physical review letters, 2002 – American Physical Society