Octaviana Datcu

Polytechnic University of Bucharest | UPB · Department of Telecommunications

This article presents a configurable, high-throughput pseudo-random number generator template targeting cryptographic applications. The template is parameterized using a chaotic map that generates data, an entropy builder that is used to periodically change the parameters of the map and a parameter change interval, which is the number of iterations...

In the recent years, the conventional lighting systems are beginning to be replaced by LED lighting systems. In a Visible Light Communication (VLC) system, the visible light is used to provide a link between a transmitter, who is typically a LED, and a receiver, which is either a photodetector or an image sensor. The VLC can be used, besides illumi...

One of the easiest to implement, yet complex, symmetric key chaos-based ciphers is the one proposed by Baptista in 1998. It has attracted much interest from scholars, who underlined its deficiencies and proposed different methods to enhance it. The present paper proposes an additional step in the encryption procedure - a modulo two sum between the...

As a continuation of previous work, where a discrete-Time Baptista-Type chaos-based cipher was implemented in a Xilinx FPGA module, this paper proposes a more complex scheme involving hybrid dynamics. A continuous chaotic evolution is utilized to dynamically and randomly change the secret key of the discrete-Time part. This work describes the desig...

It is well-known that, for nonlinear systems, the observability is often only a local property and depends on the input. Moreover, it is often required that the observer be of the same dimension as the original system. A direct consequence of this requirement is that it enlarges the set of observability singularities. If, on one hand, it is impossi...

The paper presents a steganographic method which hides a secret message in a video flow. The secret message represents the result of a chaos-based encryption scheme. One of the flaws which make the algorithm unpractical for real-time applications is that, while the elements of the plain-message are represented using 8 bits (ASCII characters) the co...

An important issue in communications, in general, and cryptography, in particular, is recovering the information of interest at the reception end. Recent techniques make use of sliding mode observers to achieve this. Another useful method to reconstruct the state space of the transmitter at the receiver end, is the singular value decomposition. Tar...

A method to overcome a correlation function based cryptanalytic attack in the case of chaos-based cryptography was proposed in the literature. The output of the transmitter, the synchronization message, was digitized and the weights of the bits of its binary representation were changed with a secret key consisting in a permutation only known by the...

The observability of a system with respect to its possible outputs is usually evaluated using the rank criterion of the observability matrix or the observability indices. In addition, this paper uses the properties of the differential equations characterizing real-time electrical circuits which base their nonlinearities on the exponential function....

When secure data transmission is implemented through chaotic systems, the choice of the output is a preliminary problem. In this paper, the quality of the transmitted information is analysed with respect to the observability concept, for each potential output. More-over, in order to overcome observability loss, a dual immersion technique is propose...

Usually, when analyzing a data series, dynamical systems theory is used to reconstruct the state space of the original system. This work aims to determine which of a chaotic system's states is best suited as output when transmitting secret messages. This is the first step prior to designing an actual communication scheme. As an example, the three s...

The present work aims to find an alternative way to the classical Lyapunov exponents of characterizing the chaotic behavior of a system. The procedures that compute Lyapunov exponents use complicated mathematical operations, such as base change and linearization of the investigated system. The main advantage of the proposed procedure is that it can...

Many studies analyze the encrypted transmission using the synchronization of chaotic signals. This requires the exchange of an analog synchronization signal, which almost always is a state of the chaotic generator. However, very few different chaotic structures are used for this purpose, still. The uniqueness of their dynamics allows the identifica...

In the '80s Takens formulated the conditions that ensure the capability to reconstruct the dynamics of a transmitter when an observer receives one scalar output from the transmitter. In practical situations, the reconstruction of the original system is strongly influenced by the choice of the variable transmitted over the communication channel. Thi...

This work proposes a new algorithm aiming to locally measure the divergence of initially nearby trajectories. The divergence is considered in the case of strange attractors, as an alternative of classical Lyapunov exponents. The new algorithm makes use of the Euclidean distance in order to define the local divergence. It is, then, possible to analy...

This article aims to experimentally prove the feasibility of an impulsive observer in order to recover the secret information embedded in a hybrid chaotic system. The first challenge of such a communication scheme is to synchronize the analog circuits that compose it. That is the stage that this article fulfils and presents.

This Thesis deals with the domain of cryptography based on hybrid chaotic dynamics.In order to increase the robustness of the security in data transmission with respect to known text attack, this work was particularly focused on two directions: the statistical approach and the automation control.The main contributions of this work are organized in...

This paper aims firstly to highlight the possibility of recovering a message included in a chaotic continuous time delay system, secondly to show that it is possible to use the third order sliding mode in order to recover directly all the states and the unknown input (message), thirdly to illustrate the robustness of the proposed observer with resp...

This paper aims to present an electronic implementation of an enciphering algorithm proposed in order to overcome the drawback of the chaotic systems described by polynomial equations when the secret key of the communication is established deriving their bifurcation parameters. The Generalized Hénon Map is the chaotic system that embeds the classic...

The paper analyzes, by original statistical, methods the minimum sampling distance that enables to extract statistically independent data sets from the generalized Hénon Map. For the statistical independence analysis, it is necessary to evaluate the entry moment of the chaotic system in the stationarity region. The statistical investigation relies...

The paper belongs to the field of chaotic based cryptography. It relies on some ideas from classical fundamentals as mixing functions suggested by C.E. Shannon for secrecy systems, and on the known publication of M.S. Baptista, a paper essentially implying the ergodicity assumption of the chaotic signal in cipher design. In this paper, the first st...