Technology and knowledge connecting university and business
Issue 14 | Year 6 | February 2016


The SiQuro system: silicon nanophotonics for crypotographic applications

Versione stampabile
by Alessandro Tomasi and Stefano Tondini
Are both research fellows in the departments of Mathematics and of Physics, respectively, at the University of Trento.
The integration of quantum photonics and microelectronics is the basis for the development of a secure communications system with applications in industry. A collaboration between the University and FBK.

From the exchange of photos or text messages to the remote reading of utility meters and to mobile contactless micropayments, there is an ever-increasing number of applications that require secure communication. 
The evolution of computing resources and the increasing efficiency of parallel computing techniques are continually exploited in order to compromise the security of such applications. 

Random number generators are the basis for estabIishing and maintaining secure channels of communication. The protocols currently used for secure communications over the internet, including chat, email and online commerce, require a robust source of random numbers in order to operate securely. Often these generators are simply computer-based algorithms, whose product is hopefully difficult, although not impossible, to predict given a large enough number of observations over time. If the initial state of the system is also known, prediction becomes trivial.

In contrast, it is physically impossible to predict the numbers generated by quantum phenomena because of their intrinsically indeterminate nature. This property, which is extremely advantageous from a security point of view, is being studied as part of the project “On silicon quantum optics for quantum computing and secure communications (SiQuro)”, one of the winners of the Grandi Progetti 2012 competition run by the Autonomous Province of Trento. The main participants are the University of Trento and the Fondazione Bruno Kessler (FBK), who are collaborating on the development of a physical random number generator that is suitable for cryptographic purposes, as well as being compact, robust, and able to be integrated into other circuits. 

To achieve this goal, it was decided to use the platform of silicon photonics, which combines integration with low energy consumption and isolation from thermal noise. Using nanotechnology, the optical properties of silicon have been engineered so that it can emit light, and at the same time, quantum theories have been developed that are able to describe this behavior. The generation of random numbers occurs through the coupling of the light source with state-of-the-art single photon detectors. 

The Nanoscience Laboratory (Nanolab) of the Department of Physics at the University of Trento, headed by Lorenzo Pavesi, coordinates the whole SiQuro project and has designed the silicon light source. The Laboratory of Industrial Mathematics and Cryptography (CryptoLabTN) at the Department of Mathematics, led by Massimiliano Sala, has developed the mathematical models and the tests for the prototypes. The IRIS and FMPS groups at the Centre for Materials and Microsystems of FBK, headed respectively by David Stoppa and Georg Pucker, have designed the sensors, the light sources, the circuit logic and the overall prototypes.  

The project has led to the development of different architectures for the generation of random numbers, for which one patent was awarded in 2015, and another patent application is in process.  
The random number generators currently on the market are too big, expensive, and susceptible to environmental conditions to be adopted on a wide scale.  In the era in which smartphone connectivity has become indispensable, from coffee machines to electric bicycles, from new generation fridges to action cams, the potential market for this product ranges from domotics to automotive applications. The potential product volumes are significant. Just think of the 7.5 million private cars sold each year in the United States, or of the number of machine-to-machine connections, which is about to overtake the number of mobile phone connections, 5 billion in 2015.  

Apart from this sector of the market, which already seems to be largely receptive, a more far-reaching idea is to use the product in smart cities. To have a city ecosystem that is energy efficient, technologically advanced in terms of services to citizens, and secure, both for people and for the community, one needs extremely effective security systems. The area of intelligent transport using remote controlled vehicles is just one of the many sectors in which the technology developed in the SiQuro project could be successfully applied. (For more details see

This first phase of the research is leading towards on-chip quantum cryptography in which the cryptographic keys are obtained from integrated random number generators and transmitted by quantum communication systems. This technology offers the advantage of enabling cryptographic processes in which it is not possible to intercept data encoded in a quantum state without modifying the quantum state itself. This will make it possible to detect whether the security of the transmission has been breached, potentially blocking the intrusion attempt.