117 research outputs found
Cryptanalyzing a discrete-time chaos synchronization secure communication system
This paper describes the security weakness of a recently proposed secure
communication method based on discrete-time chaos synchronization. We show that
the security is compromised even without precise knowledge of the chaotic
system used. We also make many suggestions to improve its security in future
versions.Comment: 11 pages, 3 figures, latex forma
The Quality of the New Generator Sequence Improvent to Spread the Color Systemâs Image Transmission
This paper shows a new technic applicable for the digital devices that are the result of the finiteâs effect precision in the chaotic dynamics used in the coupled technic and the chaotic mapâs perturbation technics used for the generation of a Pseudo-Random Number Generator (PRNGs).The use of the pseudo- chaotic sequences coupled to the orbit perturbation method in the chaotic logistic map and the NewPiece-Wise Linear Chaotic Map (NPWLCM). The pseudo random number generatorâs originality proposed from the perturbation of the chaotic recurrence. Furthermore the outputs of the binary sequences with NPWLCM are reconstructed conventionally with the Bernoulliâs sequences shifts map to change the shapes with the bitwise permetation then the results in simulation are shown in progress.After being perturbed, the chaotic system can generate the chaotic binary sequences in uniform distribution and the statistical properties invulnerable analysis. This generator also has many advantages in the possible useful applications of spread spectrum digitalimages, such as sensitive secret keys, random uniform distribution of pixels in Crypto system in secure and synchronize communication
Deterministic Chaos in Digital Cryptography
This thesis studies the application of deterministic chaos to digital
cryptography. Cryptographic systems such as pseudo-random generators
(PRNG), block ciphers and hash functions are regarded as a dynamic
system (X, j), where X is a state space (Le. message space)
and f : X -+ X is an iterated function. In both chaos theory and
cryptography, the object of study is a dynamic system that performs
an iterative nonlinear transformation of information in an apparently
unpredictable but deterministic manner. In terms of chaos theory, the
sensitivity to the initial conditions together with the mixing property
ensures cryptographic confusion (statistical independence) and diffusion
(uniform propagation of plaintext and key randomness into cihertext).
This synergetic relationship between the properties of chaotic and
cryptographic systems is considered at both the theoretical and practical
levels: The theoretical background upon which this relationship is
based, includes discussions on chaos, ergodicity, complexity, randomness,
unpredictability and entropy.
Two approaches to the finite-state implementation of chaotic systems
(Le. pseudo-chaos) are considered: (i) floating-point approximation of
continuous-state chaos; (ii) binary pseudo-chaos. An overview is given
of chaotic systems underpinning cryptographic algorithms along with
their strengths and weaknesses. Though all conventional cryposystems
are considered binary pseudo-chaos, neither chaos, nor pseudo-chaos are
sufficient to guarantee cryptographic strength and security.
A dynamic system is said to have an analytical solution Xn = (xo)
if any trajectory point Xn can be computed directly from the initial
conditions Xo, without performing n iterations. A chaotic system with an
analytical solution may have a unpredictable multi-valued map Xn+l =
f(xn). Their floating-point approximation is studied in the context of
pseudo-random generators.
A cryptographic software system E-Larm âą implementing a multistream
pseudo-chaotic generator is described. Several pseudo-chaotic
systems including the logistic map, sine map, tangent- and logarithm feedback
maps, sawteeth and tent maps are evaluated by means of floating point
computations. Two types of partitioning are used to extract
pseudo-random from the floating-point state variable: (i) combining the
last significant bits of the floating-point number (for nonlinear maps);
and (ii) threshold partitioning (for piecewise linear maps). Multi-round
iterations are produced to decrease the bit dependence and increase non-linearity.
Relationships between pseudo-chaotic systems are introduced
to avoid short cycles (each system influences periodically the states of
other systems used in the encryption session).
An evaluation of cryptographic properties of E-Larm is given using
graphical plots such as state distributions, phase-space portraits, spectral
density Fourier transform, approximated entropy (APEN), cycle length
histogram, as well as a variety of statistical tests from the National Institute
of Standards and Technology (NIST) suite. Though E-Larm passes
all tests recommended by NIST, an approach based on the floating-point
approximation of chaos is inefficient in terms of the quality/performance
ratio (compared with existing PRNG algorithms). Also no solution is
known to control short cycles.
In conclusion, the role of chaos theory in cryptography is identified;
disadvantages of floating-point pseudo-chaos are emphasized although
binary pseudo-chaos is considered useful for cryptographic applications.Durand Technology Limite
Chaotic iterations versus Spread-spectrum: chaos and stego security
A new framework for information hiding security, called chaos-security, has
been proposed in a previous study. It is based on the evaluation of
unpredictability of the scheme, whereas existing notions of security, as
stego-security, are more linked to information leaks. It has been proven that
spread-spectrum techniques, a well-known stego-secure scheme, are chaos-secure
too. In this paper, the links between the two notions of security is deepened
and the usability of chaos-security is clarified, by presenting a novel data
hiding scheme that is twice stego and chaos-secure. This last scheme has better
scores than spread-spectrum when evaluating qualitative and quantitative
chaos-security properties. Incidentally, this result shows that the new
framework for security tends to improve the ability to compare data hiding
scheme
Steganography: a class of secure and robust algorithms
This research work presents a new class of non-blind information hiding
algorithms that are stego-secure and robust. They are based on some finite
domains iterations having the Devaney's topological chaos property. Thanks to a
complete formalization of the approach we prove security against watermark-only
attacks of a large class of steganographic algorithms. Finally a complete study
of robustness is given in frequency DWT and DCT domains.Comment: Published in The Computer Journal special issue about steganograph
Joint block and stream cipher based on a modified skew tent map
Image encryption is very different from that of texts due to the bulk data capacity and the
high redundancy of images. Thus, traditional methods are difficult to use for image encryption
as their pseudo-random sequences have small space. Chaotic cryptography use chaos
theory in specific systems working such as computing algorithms to accomplish dissimilar
cryptographic tasks in a cryptosystem with a fast throughput. For higher security, encryption
is the approach to guard information and prevent its leakage. In this paper, a hybrid encryption
scheme that combines both stream and block ciphering algorithms is proposed in order
to achieve the required level of security with the minimum encryption time. This scheme is
based on an improved mathematical model to cover the defects in the previous discredited
model proposed by Masuda. The proposed chaos-based cryptosystem uses the improved
Skew Tent Map (STM) RQ-FSTM as a substitution layer. This map is based on a lookup
table to overcome various problems, such as the fixed point, the key space restrictions, and
the limitation of mapping between plain text and cipher text. It uses the same map as a generator
to change the byte position to achieve the required confusion and diffusion effects.
This modification improves the security level of the original STM. The robustness of the
proposed cryptosystem is proven by the performance and the security analysis, as well as
the high encryption speed. Depending on the results of the security analysis the proposed
system has a better dynamic key space than previous ones using STM, a double encryption
quality and a better security analysis than others in the literature with speed convenience to
real-time applications
One-Way Hash Function Based on Delay-Induced Hyperchaos
Peer reviewedPostprin
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