Véletlenszerű fluktuációk analízisén és hasznosításán alapuló mérési és titkosítási eljárások vizsgálata

Random signals - "noises" - aren’t necessarily hindrances to be eliminated, they can carry information about the examined system. They can also play a constructive role - optimal functioning of some systems are made only possible by appropriate noise application. In the dissertation results are presented in areas which are examples of utilising noises in a constructive role or as an information source. The subject of the first half of the thesis is the analysis of the Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchange protocol. First, the necessary and sufficient conditions of noise properties for unconditional security are deducted using the tools of mathematical statistics only, giving a mathematical proof for the system's perfect security. Next, the generalization of the protocol is presented, allowing the two communicating parties to use different hardware, i.e. resistors with different values. This result not only makes the practical application of the protocol much easier, but resulted in the reinterpretation of the classical physical description of the original KLJN protocol’s security . Finally the supplement of the generalized protocol is presented, in which the components previously bringing non-ideality and information leakage into the system became a part of the unconditionally secure ideal system, which is evidently a big step forward for the protocol's practical applications. Thereafter a new field of application for using fluctuations as an information source is shown. The presented results about analyzing kayak paddlers' motion signals pointed out that the quality of the paddling is correlated to the fluctuation of the period and stroke impulse, which characterise the period of the motion. Thus the temporal indicators characterizing the period fluctuations and the spectral indicators based on the raw motion signals' signal-to-noise ratio could contain extra information. The latter method of spectral variability analysis could be useful for other periodic signals as well

Dagstuhl News January - December 2011

"Dagstuhl News" is a publication edited especially for the members of the Foundation "Informatikzentrum Schloss Dagstuhl" to thank them for their support. The News give a summary of the scientific work being done in Dagstuhl. Each Dagstuhl Seminar is presented by a small abstract describing the contents and scientific highlights of the seminar as well as the perspectives or challenges of the research topic

Virtual Proofs of Reality

In this paper, we discuss the question how physical statements can be proven remotely over digital communication channels, but without using classical secret keys, and without assuming tamper-resistant and trusted measurement hardware in the location of the prover. Examples for the considered physical statements are: (i) “the temperature of a certain object is X °C”, (ii) “two certain objects are positioned at distance X”, or (iii) “a certain object has been irreversibly altered or destroyed”. In lack of an established name, we would like to call the corresponding security protocols ”virtual proofs of reality” (VPs). While a host of variants seems conceivable, this paper focuses on VPs in which the verifier has handed over one or more specific physical objects O_i to the prover at some point prior to the VP. These “witness objects” assist the prover during the proof, but shall not contain classical digital keys nor be assumed tamper-resistant in the classical sense. The prover is allowed to open, inspect and alter these objects in our adversarial model, only being limited by current technology, while he shall still be unable to prove false claims to the verifier. In order to illustrate our concept, we give example protocols built on temperature sensitive integrated circuits, disordered optical scattering media, and quantum systems. These protocols prove the temperature, destruction/modification, or relative position of witness objects in the prover’s location. Full experimental realizations of these schemes are beyond the scope of this paper. But the protocols utilize established technologies from the areas of physical unclonable functions and quantum cryptography, and hence appear plausible also without such proof. Finally, we also discuss potential advancements of our method in theory, for example “public virtual proofs” that function without exchanging witness objects Oi between the verifier and the prover. Our work touches upon and partly extends several established cryptographic and security concepts, including physical unclonable functions, quantum cryptography, and interactive proof systems

Dagstuhl News January - December 2007

"Dagstuhl News" is a publication edited especially for the members of the Foundation "Informatikzentrum Schloss Dagstuhl" to thank them for their support. The News give a summary of the scientific work being done in Dagstuhl. Each Dagstuhl Seminar is presented by a small abstract describing the contents and scientific highlights of the seminar as well as the perspectives or challenges of the research topic

Multi-factor Physical Layer Security Authentication in Short Blocklength Communication

Lightweight and low latency security schemes at the physical layer that have recently attracted a lot of attention include: (i) physical unclonable functions (PUFs), (ii) localization based authentication, and, (iii) secret key generation (SKG) from wireless fading coefficients. In this paper, we focus on short blocklengths and propose a fast, privacy preserving, multi-factor authentication protocol that uniquely combines PUFs, proximity estimation and SKG. We focus on delay constrained applications and demonstrate the performance of the SKG scheme in the short blocklength by providing a numerical comparison of three families of channel codes, including half rate low density parity check codes (LDPC), Bose Chaudhuri Hocquenghem (BCH), and, Polar Slepian Wolf codes for n=512, 1024. The SKG keys are incorporated in a zero-round-trip-time resumption protocol for fast re-authentication. All schemes of the proposed mutual authentication protocol are shown to be secure through formal proofs using Burrows, Abadi and Needham (BAN) and Mao and Boyd (MB) logic as well as the Tamarin-prover

Comments On "A New Transient Attack On The Kish Key Distribution System"

A recent IEEE Access Paper by Gunn, Allison and Abbott (GAA) proposed a new transient attack against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system. The attack is valid, but it is easy to build a defense for the KLJN system. Here we note that GAA's paper contains several invalid statements regarding security measures and the continuity of functions in classical physics. These deficiencies are clarified in our present paper, wherein we also emphasize that a new version of the KLJN system is immune against all existing attacks, including the one by GAA.Comment: Accepted for publication in the journal Metrology and Measurement Systems (May 2016