Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extended visual cryptography systems   Visual cryptography schemes have been introduced in 1994 by Naor and Shamir.
Their idea was to encode a secret image into $n$ shadow images and to give
exactly one such shadow image to each member of a group $P$ of $n$ persons.
Whereas most work in recent years has been done concerning the problem of
qualified and forbidden subsets of $P$ or the question of contrast optimizing,
in this paper we study extended visual cryptography schemes, i.e. shared secret
systems where any subset of $P$ shares its own secret.

17
The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
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The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat