We report a free-space quantum key distribution system designed for high-speed key transmission in urban areas. Clocking the system at gigahertz frequencies and efficiently filtering background enables higher secure key rates than those previously achieved by similar systems. The transmitter and receiver are located in two separate buildings 300 m apart in downtown Madrid and they exchange secure keys at rates up to 1 Mbps. The system operates in full bright daylight conditions with an average secure key rate of 0.5 Mbps and 24 h stability without human intervention.

The research leading to these results has received funding from the Ministry of Economy and Competitiveness through SEMOLA project (TEC2015-68284-R) and from the Autonomous Region of Madrid through MOSI-AGIL-CM project (grant P2013/ICE-3019, co-funded by EU Structural Funds FSE and FEDER). Borja Bordel has received funding from the Ministry of Education through the FPU program (grant number FPU15/03977). This research has been partially supported by Ministerio de Economía, Industria y Competitividad (MINECO), Agencia Estatal de Investigación (AEI), and Fondo Europeo de Desarrollo Regional (FEDER, UE) under project COPCIS, reference TIN2017-84844-C2-1-R. Future 5G networks must provide communication services to a great and heterogeneous collection of scenarios: from traditional mobile communications, to emerging applications such as Industry 4.0 or the Internet-of-Things (IoT). In this context, the network slicing technique is defined, where network resources are packaged and assigned in an isolated manner to sets of users according to their specific requirements. Two different domains are, thus, defined: the intra-slice domain (where dedicated and specific solutions have to be deployed) and the inter-slice domain (including transversal solutions). One of the key topics which should be redefined following this approach is security. Traditionally, some solutions (such as stream ciphers) were not considered in mobile networks. However, 5G systems will be extensively employed in other new and very distinct scenarios, where requirements are different. For example, the use of resource constrained devices with little mobility and real-time data streaming in certain IoT applications suggests the use of stream ciphers (and other similar techniques) as main security solutions. Therefore, in this paper we investigate and propose a new security solution for emerging 5G networks, to be applied in the intra-slice domain. The proposed solutions employ lightweight pseudo-random number generators in order to provide the keystream used in stream ciphers which protect the private information and hide the communication signals in the frequency spectrum using spread spectrum techniques. We also describe and evaluate a first implementation of the proposed solution, using both, a simulation scenario and a real deployment.

Lightweight cryptography aims to address the security demands in resource-constrained hardware and software environments, such as the Internet of Things (IoT). These constraints severely limit solutions offered by conventional cryptographic primitives, which turn too expensive to achieve. In this paper, a lightweight pseudorandom number generator that fits the IoT demands is presented. It has a good performance on Atmel 8-bit AVR and Intel Curie 32-bit microcontrollers. The analysis of the hardware complexity in terms of gate equivalent confirms that it is suitable for the IoT.