4,234 research outputs found
Breaking a chaos-based secure communication scheme designed by an improved modulation method
Recently Bu and Wang [Chaos, Solitons & Fractals 19 (2004) 919] proposed a
simple modulation method aiming to improve the security of chaos-based secure
communications against return-map-based attacks. Soon this modulation method
was independently cryptanalyzed by Chee et al. [Chaos, Solitons & Fractals 21
(2004) 1129], Wu et al. [Chaos, Solitons & Fractals 22 (2004) 367], and
\'{A}lvarez et al. [Chaos, Solitons & Fractals, accepted (2004),
arXiv:nlin.CD/0406065] via different attacks. As an enhancement to the Bu-Wang
method, an improving scheme was suggested by Wu et al. by removing the
relationship between the modulating function and the zero-points. The present
paper points out that the improved scheme proposed by Wu et al. is still
insecure against a new attack. Compared with the existing attacks, the proposed
attack is more powerful and can also break the original Bu-Wang scheme.
Furthermore, it is pointed out that the security of the modulation-based
schemes is not so satisfactory from a pure cryptographical point of view. The
synchronization performance of this class of modulation-based schemes is also
discussed.Comment: elsart.cls, 18 pages, 9 figure
Return-Map Cryptanalysis Revisited
As a powerful cryptanalysis tool, the method of return-map attacks can be
used to extract secret messages masked by chaos in secure communication
schemes. Recently, a simple defensive mechanism was presented to enhance the
security of chaotic parameter modulation schemes against return-map attacks.
Two techniques are combined in the proposed defensive mechanism: multistep
parameter modulation and alternative driving of two different transmitter
variables. This paper re-studies the security of this proposed defensive
mechanism against return-map attacks, and points out that the security was much
over-estimated in the original publication for both ciphertext-only attack and
known/chosen-plaintext attacks. It is found that a deterministic relationship
exists between the shape of the return map and the modulated parameter, and
that such a relationship can be used to dramatically enhance return-map attacks
thereby making them quite easy to break the defensive mechanism.Comment: 11 pages, 7 figure
Lorenz System Parameter Determination and Application to Break the Security of Two-channel Chaotic Cryptosystems
This paper describes how to determine the parameter values of the chaotic
Lorenz system used in a two-channel cryptosystem. The geometrical properties of
the Lorenz system are used firstly to reduce the parameter search space, then
the parameters are exactly determined, directly from the ciphertext, through
the minimization of the average jamming noise power created by the encryption
process.Comment: 5 pages, 5 figures Preprint submitted to IEEE T. Cas II, revision of
authors name spellin
Secure communication based on indirect coupled synchronization
In this paper, a secure communication system composed of four chaotic oscillators is proposed. Two of these oscillators are unidirectionally coupled and employed as transmitter and receiver. The other two oscillators are indirectly coupled and are employed as keystream generators. The novelty lies in the generation of the same chaotic keystream both in the transmitter and receiver side for encryption and decryption purposes. We show, in particular, that it is possible to synchronize the two keystream generators even though they are not directly coupled. So doing, an estimation of the keystream is obtained allowing decrypting the message. The main feature of the proposed communication scheme is that the keystream cannot be generated with the sole knowledge of the transmitted chaotic signal, hence making it very secure. The performance of the proposed communication scheme is shown via simulation using the Chua and Lorenz oscillators
Implementation of a secure digital chaotic communication scheme on a DSP board
In this paper, a new a secure communication scheme using chaotic signal for transmitting binary digital signals is proposed and which is then implemented on a Digital Signal Processor (DSP) board. The method uses the idea of indirect coupled synchronization for generating the same keystream in the transmitter and receiver side. This chaotic keystream is applied to encrypt the message signal before being modulated with a chaotic carrier generated from the transmitter. Discrete chaotic maps, 3D Henon map and Lorenz system are used as transmitter/receiver and key generators respectively. The overall system is experimentally implemented in the TMS320C6713 DSK board using code composer and Simulink showing the successful message extraction thus proving the feasibility of the system in the DSP board
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