Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perspective -- On the thermodynamics of perfect unconditional security   A secure key distribution (exchange) scheme is unconditionally secure if it
is unbreakable against arbitrary technological improvements of computing power
and/or any development of new algorithms. There are only two families of
experimentally realized and tested unconditionally secure key distribution
technologies: Quantum Key Distribution (QKD), the base of quantum cryptography,
which utilizes quantum physical photonic features; and the
Kirchhoff-Law-Johnson-Noise (KLJN) system that is based on classical
statistical physics (fluctuation-dissipation theorem). The focus topic of this
paper is the thermodynamical situation of the KLJN system. In all the original
works, the proposed KLJN schemes required thermal equilibrium between the
devices of the communicating parties to achieve perfect security. However,
Vadai, et al, in (Nature) Science Reports 5 (2015) 13653 shows a modified
scheme, where there is a non-zero thermal noise energy flow between the
parties, yet the system seems to resist all the known attack types. We
introduce a new attack type against their system. The new attack utilizes
coincidence events between the line current and voltages. We show that there is
non-zero information leak toward the Eavesdropper, even under idealized
conditions. As soon as the thermal equilibrium is restored, the system becomes
perfectly secure again. In conclusion, perfect unconditional security requires
thermal equilibrium.

5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga