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Unconditional security by the laws of classical physics

Mingesz R., Kish L. B., Gingl Z., Granqvist C.-G., Wen H., Peper F., Eubanks T., Schmera G.

Metrology and Measurement Systems

2013

Vol. 20, nr 1

3-16

There is an ongoing debate about the fundamental security of existing quantum key exchange schemes. This debate indicates not only that there is a problem with security but also that the meanings of perfect, imperfect, conditional and unconditional (information theoretic) security in physically secure key exchange schemes are often misunderstood. It has been shown recently that the use of two pairs of resistors with enhanced Johnsonnoise and a Kirchhoff-loop - i.e., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol . for secure key distribution leads to information theoretic security levels superior to those of today's quantum key distribution. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer-reviewed publications. The KLJN system is briefly surveyed here with discussions about the essential questions such as (i) perfect and imperfect security characteristics of the key distribution, and (ii) how these two types of securities can be unconditional (or information theoretical).

Embedding Universal Delay-Insensitive Circuits in Asynchronous Cellular Spaces

Lee J., Adachi S., Peper F., Morita K.

Fundamenta Informaticae

2003

Vol. 58, nr 3,4

295--320

Asynchronous Cellular Automata (ACA) are cellular automata which allow cells to be updated at times that are random and independent of each other. Due to their unpredictable behavior, ACA are usually dealt with by simulating a timing mechanism that forces all cells into synchronicity. Though this allows the use of well-established synchronous methods to conduct computations, it comes at the price of an increased number of cell states. This paper presents a more effective approach based on a 5-state ACA with von Neumann neighborhood that uses rotation- and reflection-symmetric transition rules to describe the interactions between cells. We achieve efficient computation on this model by embedding so-called Delay-Insensitive circuits in it, a type of asynchronous circuits in which signals may be subject to arbitrary delays, without this being an obstacle to correct operation. Our constructions not only imply the computational universality of the proposed cellular automaton, but also allow the efficient use of its massive parallelism, in the sense that the circuits operate in parallel and there are no signals running around indefinitely in the circuits in the absence of input.