Authenticated Timing Protocol Based on Galileo ACAS.

Global navigation satellite systems (GNSSs) provide accurate positioning and timing services in a large gamut of sectors, including financial institutions, Industry 4.0, and Internet of things (IoT). Any industrial system involving multiple devices interacting and/or coordinating their functionalities needs accurate, dependable, and trustworthy time synchronization, which can be obtained by using authenticated GNSS signals. However, GNSS vulnerabilities to time-spoofing attacks may cause security issues for their applications. Galileo is currently developing new services aimed at providing increased security and robustness against attacks, such as the open service navigation message authentication (OS-NMA) and commercial authentication service (CAS). In this paper, we propose a robust and secure timing protocol that is independent of external time sources, and solely relies on assisted commercial authentication service (ACAS) and OS-NMA features. We analyze the performance of the proposed timing protocol and discuss its security level in relation to malicious attacks. Lastly, experimental tests were conducted to validate the proposed protocol.

Free-space optical channel estimation for physical layer security.

We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security.

Experimental quantum key distribution with finite-key security analysis for noisy channels.

In quantum key distribution implementations, each session is typically chosen long enough so that the secret key rate approaches its asymptotic limit. However, this choice may be constrained by the physical scenario, as in the perspective use with satellites, where the passage of one terminal over the other is restricted to a few minutes. Here we demonstrate experimentally the extraction of secure keys leveraging an optimal design of the prepare-and-measure scheme, according to recent finite-key theoretical tight bounds. The experiment is performed in different channel conditions, and assuming two distinct attack models: individual attacks or general quantum attacks. The request on the number of exchanged qubits is then obtained as a function of the key size and of the ambient quantum bit error rate. The results indicate that viable conditions for effective symmetric, and even one-time-pad, cryptography are achievable.

A lattice estimation approach for the automatic evaluation of corneal endothelium density.

The analysis of microscopy images of corneal endothelium is routinely carried out at eye banks to assess cell density, one of the main indicators of cornea health state and quality. We propose here a new method to derive endothelium cell density that, at variance with most of the available techniques, does not require the identification of cell contours. It exploits the feature that endothelium cells are approximately laid out as a regular tessellation of hexagonal shapes. This technique estimates the inverse transpose of a matrix generating this cellular lattice, from which the density is easily obtained. The algorithm has been implemented in a Matlab prototype and tested on a set of 21 corneal endothelium images. The cell densities obtained matched quite well with the ones manually estimated by eye-bank experts: the percent difference between them was on average -0.1% (6.5% for absolute values). Albeit the performances of this new algorithm on the images of our test set are definitely good, a careful evaluation on a much larger data set is needed before any clinical application of the proposed technique could be envisaged. The collection of an adequate number of endothelium images and of their manual densities is currently in progress.