Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Unicity Distance of Stego Key   Steganography is about how to send secret message covertly. And the purpose
of steganalysis is to not only detect the existence of the hidden message but
also extract it. So far there have been many reliable detecting methods on
various steganographic algorithms, while there are few approaches that can
extract the hidden information. In this paper, the difficulty of extracting
hidden information, which is essentially a kind of privacy, is analyzed with
information-theoretic method in the terms of unicity distance of steganographic
key (abbreviated stego key). A lower bound for the unicity distance is
obtained, which shows the relations between key rate, message rate, hiding
capacity and difficulty of extraction. Furthermore the extracting attack to
steganography is viewed as a special kind of cryptanalysis, and an effective
method on recovering the stego key of popular LSB replacing steganography in
spatial images is presented by combining the detecting technique of
steganalysis and correlation attack of cryptanalysis together. The analysis for
this method and experimental results on steganographic software ``Hide and Seek
4.1" are both accordant with the information-theoretic conclusion.

36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ