# The Rise of Quantum Information and Communication Technologies
## 3 Management and Control of QKD Networks  
In context of the Euro-QCI initiative ([[https://digital-strategy.ece.europa.eu/en/policies/european-quantum-communication-infrastructure-euroqci](https://digital-strategy.ece.europa.eu/en/policies/european-quantum-communication-infrastructure-euroqci)]([https://digital-strategy.ece.europa.eu/en/policies/european-quantum-communication-infrastructure-euroqci](https://digital-strategy.ece.europa.eu/en/policies/european-quantum-communication-infrastructure-euroqci)), accessed on 10 December 2023) (Euro Quantum Communication Infrastructure), the project EQUO is contributing to the realization of a European industrial ecosystem for secure QCI technologies and systems. EQUO's main focus is the industrialization of European QKD solutions ready for deployment, realizing high-TRLs [8,9] and high-performance technology components like the quantum random number generator and single photon detector as examples. Indeed, system integration from the QKD system to telecommunication networks providing high-level security encryption together with suitable key management represents the key to the application of the whole designed system in real scenarios, assuring interoperability between quantum and traditional cybersecurity systems and protecting sensitive digital data. Achieving the TRLs [8,9] necessarily requires the design and development of a control and management architecture for the QKD network (QKDN). EQUO architectural solutions are compliant (by design) to the most relevant international recommendations (ITU-T, Y.38 xx \"Quantum Key Distribution Networks\" series) and European standard (ETSI, Group Specification documents on QKD), to maximize interoperability both between QKDN components (e.g., QKD module, key manager, QKD controller, QKD manager and cryptographic application) and between different QKDNs. The functional architecture of the QKDN, designed and implemented in a metropolitan use case, is shown in Figure 1. This architectural model is derived from the recommendation ITU-T Y.3800 \"Overview on networks supporting quantum key distribution\" [10] and subsequent recommendations, ITU-T Y.3801 \"Functional requirements for quantum key distribution networks\" [11], ITU-T Y.3802 \"Quantum key distribution networks--Functional architecture\" [12], ITU-T Y.3803 \"Quantum key distribution networks--Key management\" [13] and ITU-T Y.3804 \"Quantum key distribution networks--Control and management\" [14]. Figure 1: EQUO QKDN functional architecture. The functional architecture also takes into consideration the standards ETSI GS QKD 014 \"Quantum Key Distribution (QKD); Protocol and data format of REST-based key delivery API\" [15] and ETSI GS QKD 015 \"Quantum Key Distribution (QKD); Control Interface for Software Defined Networks\" [16]. As extracted from the above-mentioned ITU-T recommendations, a QKDN functional architecture is composed of the following functional layers:  
* A quantum Layer--In this layer, each pair of QKD modules connected by a QKD link generates symmetric random bit strings in its own way. Each QKD module pushes the random bit strings up to a key manager (KM) that is in the same QKD node. Each QKD module can also send QKD link parameters (e.g., quantum bit error rates--QBERs, etc.) to the QKDN manager. * A key management layer--This layer includes KMs and KM links. Each KM is located in a QKD node. The KM performs key management. The KMs are connected via KM links. The KM receives random bit strings from QKD module(s) located in the same QKD node. The KM synchronizes and re-formats these bit strings and stores them as keys in the storage. Interfaces for various cryptographic applications are installed into the KM. The KM receives key requests from a cryptographic application, acquires the necessary number of keys from storage, synchronizes and authenticates the acquired keys via a KM link, and supplies them in an appropriate format to the cryptographic application.