Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Secure Variant of the Hill Cipher   The Hill cipher is a classical symmetric encryption algorithm that succumbs
to the know-plaintext attack. Although its vulnerability to cryptanalysis has
rendered it unusable in practice, it still serves an important pedagogical role
in cryptology and linear algebra. In this paper, a variant of the Hill cipher
is introduced that makes the Hill cipher secure while it retains the
efficiency. The proposed scheme includes a ciphering core for which a
cryptographic protocol is introduced.

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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: q-alg