GMV will play an important role in the viability study for the Caramuel project, which is the world’s first mission on the use of geostationary satellite communications for quantum key distribution (QKD). This is one of the technologies that will come to define secure information transfers in the future. The study has funding from the European Space Agency (ESA) through its ARTES 4S project (Advanced Research in Telecommunications Systems – Space Systems for Safety & Security), as well as backing from a group of Spanish companies and entities known for their international presence, led by Hispasat. One of these companies is GMV, which is contributing its expertise to the future Caramuel ground segment.

Quantum computers provide a much higher level of computing power than conventional computers. This is essential for addressing certain issues, such as decomposition into the prime factors that are the basis for current asymmetric cryptography methods. However, this power also makes a paradigm shift essential for secure communications, because hackers with quantum computers will otherwise be able to unencrypt the methods currently used in a matter of seconds. This is why it has become critical to develop a system that will allow sending of information with the necessary security safeguards, for purposes of governmental communications (civilian and military), as well as for the messages used to manage critical infrastructure elements. The system will also be applicable to a broader range of applications and services of economic, environmental, and technological interest, and those of interest to large corporations.

More secure communications

Currently, the system used for quantum key distribution relies upon optical communication, because it can be confirmed with certainty that messages sent in this way have not been intercepted. This is because integrity can be continuously verified thanks to the quantum properties of the photons. However, ground networks, such as those based on fiber-optics, can only maintain that integrity over distances of less than 100 km, because over longer distances they suffer from higher levels of signal loss.

On the other hand, when satellites are used for purposes of quantum key distribution, longer distances can be covered because much lower levels of signal loss occur when information is traveling through space. By using satellites in geostationary orbits at an altitude of 35,786 km, communications covering entire continents can be established via a single satellite, in a continuous manner and with no need for signal monitoring.

The Caramuel system includes a geostationary satellite with a quantum payload, combined with its associated ground segment. GMV is now the leader for essential work packages in the initial phase of the viability study. The satellite payload includes a high-precision telescope, a photon source that is able to send single-photon transmissions to Earth in order to preserve the associated quantum properties and all of the associated electronics. The ground segment consists of the control center and the user’s optical stations. The primary purpose of the control center is to supervise and monitor the Caramuel system as a whole, including the onboard system and the network of ground stations. In turn, the ground stations consist of two parts: an optical part with telescopes (with apertures between 80 and 180 cm) and cryogenic receivers that are able to detect individual photons; and another part responsible for distilling the keys, managing and storing them securely, and making the connection with the ground quantum network. 

The most sensitive users of the Caramuel system will be able to maintain their own telescopes to ensure that they have the highest level of security, which also means that they will not have to rely upon any intervening ground networks. On the other hand, commercial users that do not need their own telescopes can be integrated into the ground quantum network at a lower cost, with their signals then arriving at one of the nodes with a telescope owned by a service provider. This will let them connect to other nodes via satellite, whether those nodes are owned by the same provider or a different one. In this way, a global network is created.

This is how the Caramuel system is integrated with ground infrastructure to provide a cryptographic quantum key distribution service that is both seamless and transparent for its end users. As a proof of concept for this mission, a quantum key distribution connection will be established via satellite between two nodes that are in turn connected through ground infrastructure to the signal’s emitters and receivers (i.e., the users who want to share a key so that they can securely encrypt their messages).

Under Hispasat’s leadership, GMV will be participating in the Caramuel viability study along with other companies such as Alter, Banco Santander, BBVA, Cellnex, Das Photonics, Indra, Oesia, Quside, Sener, Telefónica, and Thales Alenia Space España, as well as a variety of Spanish institutions and universities including the National Cryptology Center (CCN), Center for Advanced Scientific Research (CSIC), Canary Islands Astrophysics Institute (IAC), Institute for Photonic Sciences (ICFO), National Technical Aerospace Institute (INTA), Madrid Polytechnic University (UPM), and University of Vigo (UV).

Caramuel, a major contribution to European space security

In June 2019, the European Commission (EC) announced its European Quantum Communication Infrastructure (EuroQCI) Declaration and during the next few years the first quantum communication nodes will be rolled out in various European Union countries. These nodes, which cover specific metropolitan areas, will be connected to each other via satellite to enhance their resilience. These EuroQCI satellite connections will therefore be one of the missions of the secure satellite communications system being promoted by the EC. With the Caramuel project, Spain will be making a major contribution to these European initiatives.

The Caramuel viability studies, which formally began in May after some preliminary analyses had first been performed, are expected to be finalized in October of this year. Currently, work is being performed on preliminary definition of the quantum key distribution system, specifically its end-to-end architecture. The prioritized objectives at this point are integration with the ground quantum network, and analysis of actual use cases, performed in collaboration with representatives of the banking industry and ground operators. In turn, the prioritized objective of the Caramuel project is adaptation to existing quantum communication standards, such as those produced by the International Telecommunication Union (ITU) and European Telecommunications Standards Institute (ETSI).