6,652 research outputs found
Optimal quantitative cryptanalysis of permutation-only multimedia ciphers against plaintext attacks
Recently, an image scrambling encryption algorithm of pixel bit based on
chaos map was proposed. Considering the algorithm as a typical binary image
scrambling/permutation algorithm exerting on plaintext of size ,
this paper proposes a novel optimal method to break it with some
known/chosen-plaintexts. The spatial complexity and computational complexity of
the attack are only and respectively,
where is the number of known/chosen-plaintexts used. The method can be
easily extended to break any permutation-only encryption scheme exerting on
plaintext of size and with different levels of values. The
corresponding spatial complexity and computational complexity are only
and respectively. In addition, some
specific remarks on the performance of the image scrambling encryption
algorithm are presented.Comment: 11 pages, 6 figure
An Improved Timestamp-Based Password Authentication Scheme Using Smart Cards
With the recent proliferation of distributed systems and networking, remote
authentication has become a crucial task in many networking applications.
Various schemes have been proposed so far for the two-party remote
authentication; however, some of them have been proved to be insecure. In this
paper, we propose an efficient timestamp-based password authentication scheme
using smart cards. We show various types of forgery attacks against a
previously proposed timestamp-based password authentication scheme and improve
that scheme to ensure robust security for the remote authentication process,
keeping all the advantages that were present in that scheme. Our scheme
successfully defends the attacks that could be launched against other related
previous schemes. We present a detailed cryptanalysis of previously proposed
Shen et. al scheme and an analysis of the improved scheme to show its
improvements and efficiency.Comment: 6 page
Cryptanalysis of an Encryption Scheme Based on Blind Source Separation
Recently Lin et al. proposed a method of using the underdetermined BSS (blind
source separation) problem to realize image and speech encryption. In this
paper, we give a cryptanalysis of this BSS-based encryption and point out that
it is not secure against known/chosen-plaintext attack and chosen-ciphertext
attack. In addition, there exist some other security defects: low sensitivity
to part of the key and the plaintext, a ciphertext-only differential attack,
divide-and-conquer (DAC) attack on part of the key. We also discuss the role of
BSS in Lin et al.'s efforts towards cryptographically secure ciphers.Comment: 8 pages, 10 figures, IEEE forma
Short expressions of permutations as products and cryptanalysis of the Algebraic Eraser
On March 2004, Anshel, Anshel, Goldfeld, and Lemieux introduced the
\emph{Algebraic Eraser} scheme for key agreement over an insecure channel,
using a novel hybrid of infinite and finite noncommutative groups. They also
introduced the \emph{Colored Burau Key Agreement Protocol (CBKAP)}, a concrete
realization of this scheme.
We present general, efficient heuristic algorithms, which extract the shared
key out of the public information provided by CBKAP. These algorithms are,
according to heuristic reasoning and according to massive experiments,
successful for all sizes of the security parameters, assuming that the keys are
chosen with standard distributions.
Our methods come from probabilistic group theory (permutation group actions
and expander graphs). In particular, we provide a simple algorithm for finding
short expressions of permutations in , as products of given random
permutations. Heuristically, our algorithm gives expressions of length
, in time and space . Moreover, this is provable from
\emph{the Minimal Cycle Conjecture}, a simply stated hypothesis concerning the
uniform distribution on . Experiments show that the constants in these
estimations are small. This is the first practical algorithm for this problem
for .
Remark: \emph{Algebraic Eraser} is a trademark of SecureRF. The variant of
CBKAP actually implemented by SecureRF uses proprietary distributions, and thus
our results do not imply its vulnerability. See also arXiv:abs/12020598Comment: Final version, accepted to Advances in Applied Mathematics. Title
slightly change
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