Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A simple proof of the unconditional security of relativistic quantum
  cryptography   A simple proof of the unconditional security of a relativistic quantum
cryptosystem based on orthogonal states is proposed. Restrictions imposed by
special relativity allow to substantially simplify the proof compared with the
non-relativistic cryptosystems involving non-orthogonal states. Important for
the proposed protocol is the spatio-temporal structure of the quantum states
which is actually ignored in the non-relativistic protocols employing only the
structure of the state space of the information carriers. As a consequence, the
simplification arises because of the inefficiency of collective measurements
which constitute the major problem in the non-relativistic case.

33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int