Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cryptanalysis of a chaotic block cipher with external key and its
  improved version   Recently, Pareek et al. proposed a symmetric key block cipher using multiple
one-dimensional chaotic maps. This paper reports some new findings on the
security problems of this kind of chaotic cipher: 1) a number of weak keys
exists; 2) some important intermediate data of the cipher are not sufficiently
random; 3) the whole secret key can be broken by a known-plaintext attack with
only 120 consecutive known plain-bytes in one known plaintext. In addition, it
is pointed out that an improved version of the chaotic cipher proposed by Wei
et al. still suffers from all the same security defects.

17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th