Final Report Summary - APLOE (Applied Physical Layer Orthogonal frequency division multiplexing Encryption)
Project Context and Objectives:
Security in the exchange of information has been primarily treated as an inherently applied subject, despite the theoretical formulation of perfect secrecy by Shannon in 1946. In actual networks, security commonly relies on cryptographic algorithms implemented at upper layers of the protocol stack. Recently, a compelling complementary approach for enhancing the securing of wireless systems has risen from the area of information theory and has become a focal point of research in the wireless community.
The breakthrough concept of physical layer security is to exploit the characteristics of the wireless medium such as fading or noise to ensure secrecy in wireless transmissions. Seminal earlier analyses that investigated security aspects of the wiretap channel and the broadcast channel with confidential messages have established that a noisy communication channel can offer opportunities for perfectly secure exchange of information.
In this setting, the performance measure of interest, the secrecy capacity (SC), was defined as the largest communication rate for which encoding schemes exist that simultaneously guarantee reliability in the exchange of information with a legitimate user and perfect secrecy with respect to an eavesdropper. It has been demonstrated that the SC is strictly positive when the wiretap channel is on average a degraded version of the main channel. Similar results were obtained for wireless fading channels and multiple input multiple output (MIMO) systems.
The APLOE project contributed important results in four major areas of research on physical layer security (PLS): In particular, the APLOE PIOF-GA-2010-274723 project generated significant outputs in the following areas of research:
1. Physical layer encryption for OFDM systems – Masked-OFDM systems: The first line of research of the APLOE project concerned the investigation of physical layer encryption for orthogonal frequency division multiplexing (OFDM) signals. We proposed a scheme termed Masked-OFDM in which OFDM signals are encrypted through faster than Nyquist signalling.
2. Security based on asymmetric reception – The APLOE research team has established that in networks with asymmetries in (i) the mobility of the nodes, (ii) the number of legitimate users and eavesdroppers, (iii) the circuit imperfections of the intended destination and eavesdropping receivers, it is possible to employ PLS techniques while retaining transmission rates compatible with actual applications.
3. Security through cooperation and adaptation – The APLOE research team has characterized the achievable secrecy rates of commonly used discrete alphabet systems (e.g. M-ary quadrature amplitude modulation (M-QAM) systems).
4. Security in active attacks – The PLS literature examined predominantly passive attacks, i.e. interception of a wiretap or a broadcast channel. The APLOE MC fellow has initiated and coordinated investigations regarding the achievable secrecy rates in systems with active attacks. In the investigated scenarios the active eavesdropper realizes the attack by providing false feedback (such scenarios are subcases of the Byzantine type of attacks).
The APLOE research project studied the potential of securing OFDM and multiuser wireless systems without relying on common cryptographic measures and investigated the development of friendly jamming technologies that can be used for provably secret exchange of data. Accordingly, the project’s vision was to pave the way for pragmatic proposals of PLS systems. The APLOE project excelled in all of its research objectives and helped significantly in transforming previous knowledge in the PLS area towards more practical ends. As result, the APLOE project had a significant impact:
a. In socioeconomic terms: Improvements to the security of the ICT sector are essential for the maintenance of our quality of life as well as the enhancement of the prosperity and the developmental prospects of the EU economy. Most importantly, as the critical infrastructures have become more and more dependent on public and private networks, the potential for widespread impact resulting from interception and disruption of these networks has also increased. The APLOE project has contributed by investigating the feasibility of PLS techniques in realistic networks.
b. In academic terms: From an academic point of view, this work has contributed in maintaining EU’s excellence in wireless communications, information theory, system design and security studies. Significantly, the project’s international dimension as mirrored though the fellow’s mobility actions and collaborations helped strengthen the visibility and the international impact of the European research area (ERA).
c. From an end-user point of view: This work is of interest to a wide range of European businesses and companies. The proposed novel technologies for securing wireless networks and ensuring data confidentiality in the transmission of confidential data can boost the public trust in e-commerce, e-business, e-government, e-healthcare and banking networks and applications.
Further details concerning the research team, the contributions and publications and the funding details can be found on the project’s website, www.aploe.eu