Proposta e modelagem de comunicação segura para redes veiculares (VANETS)

Pós-graduação em Ciência da Computação - IBILCE

Informação quântica e relatividade

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Entropy effect in quantum computing and information: an open-source environment simulation

The technologies are rapidly developing, but some of them present in the computers, as for instance their processing capacity, are reaching their physical limits. It is up to quantum computation offer solutions to these limitations and issues that may arise. In the field of information security, encryption is of paramount importance, being then the development of quantum methods instead of the classics, given the computational power offered by quantum computing. In the quantum world, the physical states are interrelated, thus occurring phenomenon called entanglement. This study presents both a theoretical essay on the merits of quantum mechanics, computing, information, cryptography and quantum entropy, and some simulations, implementing in C language the effects of entropy of entanglement of photons in a data transmission, using Von Neumann entropy and Tsallis entropy.

Bit-parallel coprocessor for standard ECC-GF(2m) on FPGA

This paper presents the design of a high-speed coprocessor for Elliptic Curve Cryptography over binary Galois Field (ECC- GF(2m)). The purpose of our coprocessor is to accelerate the scalar multiplication performed over elliptic curve points represented by affine coordinates in polynomial basis. Our method consists of using elliptic curve parameters over GF(2163) in accordance with international security requirements to implement a bit-parallel coprocessor on field-programmable gate-array (FPGA). Our coprocessor performs modular inversion by using a process based on the Stein's algorithm. Results are presented and compared to results of other related works. We conclude that our coprocessor is suitable for comparing with any other ECC-hardware proposal, since its speed is comparable to projective coordinate designs.

Inserção e extração de marca d'água em imagens digitais usando a transformada wavelet

Pós-graduação em Engenharia Elétrica - FEIS

Criptografia: uma nova proposta de ensino de matemática no ciclo básico

Pós-graduação em Matemática em Rede Nacional - IBILCE

Análise de desempenho dos codecs suportados pelo Asterisk com e sem criptografia

The main objective is to analyze the performance of some codecs supported by Asterisk with and without encryption using RTP and SRTP, respectively, providing important data for decision-making in the implementation of a VoIP system with Asterisk. Thus, it is possible to realize both codecs as the protocol can be chosen depending on the application, or the system's main feature is the speed packet switching, security level or lower tolerance for unsuccessful calls. For this, tests were made with the codec with and without the use of cryptography to obtain some findings on the use of the same, giving more attention to the response time for the start of a call.

O uso de elementos da criptografia como estímulo matemático na sala de aula

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hierarchy-Based Access Control in Distributed Environments

Access control is a fundamental concern in any system that manages resources, e.g., operating systems, file systems, databases and communications systems. The problem we address is how to specify, enforce, and implement access control in distributed environments. This problem occurs in many applications such as management of distributed project resources, e-newspaper and payTV subscription services. Starting from an access relation between users and resources, we derive a user hierarchy, a resource hierarchy, and a unified hierarchy. The unified hierarchy is then used to specify the access relation in a way that is compact and that allows efficient queries. It is also used in cryptographic schemes that enforce the access relation. We introduce three specific cryptography based hierarchical schemes, which can effectively enforce and implement access control and are designed for distributed environments because they do not need the presence of a central authority (except perhaps for set- UP).

O uso de elementos da criptografia como estímulo matemático na sala de aula

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Revisiting the Security of the ALRED Design and Two of Its Variants: Marvin and LetterSoup

The ALRED construction is a lightweight strategy for constructing message authentication algorithms from an underlying iterated block cipher. Even though this construction's original analyses show that it is secure against some attacks, the absence of formal security proofs in a strong security model still brings uncertainty on its robustness. In this paper, aiming to give a better understanding of the security level provided by different authentication algorithms based on this design strategy, we formally analyze two ALRED variants-the MARVIN message authentication code and the LETTERSOUP authenticated-encryption scheme,-bounding their security as a function of the attacker's resources and of the underlying cipher's characteristics.

Java Cryptographic Library for Smartphones

A JME-compliant cryptographic library for mobile application development is introduced in this paper. The library allows cryptographic protocols implementation over elliptic curves with different security levels and offers symmetric and asymmetric bilinear pairings operations, as Tate, Weil, and Ate pairings.

Cryptanalysis of an efficient three-party password-based key exchange scheme

Three-party password-authenticated key exchange (3PAKE) protocols allow entities to negotiate a secret session key with the aid of a trusted server with whom they share a human-memorable password. Recently, Lou and Huang proposed a simple 3PAKE protocol based on elliptic curve cryptography, which is claimed to be secure and to provide superior efficiency when compared with similar-purpose solutions. In this paper, however, we show that the solution is vulnerable to key-compromise impersonation and offline password guessing attacks from system insiders or outsiders, which indicates that the empirical approach used to evaluate the scheme's security is flawed. These results highlight the need of employing provable security approaches when designing and analyzing PAKE schemes. Copyright (c) 2011 John Wiley & Sons, Ltd.

Chaotic encryption method based on life-like cellular automata

A chaotic encryption algorithm is proposed based on the "Life-like" cellular automata (CA), which acts as a pseudo-random generator (PRNG). The paper main focus is to use chaos theory to cryptography. Thus, CA was explored to look for this "chaos" property. This way, the manuscript is more concerning on tests like: Lyapunov exponent, Entropy and Hamming distance to measure the chaos in CA, as well as statistic analysis like DIEHARD and ENT suites. Our results achieved higher randomness quality than others ciphers in literature. These results reinforce the supposition of a strong relationship between chaos and the randomness quality. Thus, the "chaos" property of CA is a good reason to be employed in cryptography, furthermore, for its simplicity, low cost of implementation and respectable encryption power. (C) 2012 Elsevier Ltd. All rights reserved.

ANALYSIS AND VISUALIZATION OF FLOW FIELDS USING INFORMATION-THEORETIC TECHNIQUES AND GRAPH-BASED REPRESENTATIONS

Three-dimensional flow visualization plays an essential role in many areas of science and engineering, such as aero- and hydro-dynamical systems which dominate various physical and natural phenomena. For popular methods such as the streamline visualization to be effective, they should capture the underlying flow features while facilitating user observation and understanding of the flow field in a clear manner. My research mainly focuses on the analysis and visualization of flow fields using various techniques, e.g. information-theoretic techniques and graph-based representations. Since the streamline visualization is a popular technique in flow field visualization, how to select good streamlines to capture flow patterns and how to pick good viewpoints to observe flow fields become critical. We treat streamline selection and viewpoint selection as symmetric problems and solve them simultaneously using the dual information channel [81]. To the best of my knowledge, this is the first attempt in flow visualization to combine these two selection problems in a unified approach. This work selects streamline in a view-independent manner and the selected streamlines will not change for all viewpoints. My another work [56] uses an information-theoretic approach to evaluate the importance of each streamline under various sample viewpoints and presents a solution for view-dependent streamline selection that guarantees coherent streamline update when the view changes gradually. When projecting 3D streamlines to 2D images for viewing, occlusion and clutter become inevitable. To address this challenge, we design FlowGraph [57, 58], a novel compound graph representation that organizes field line clusters and spatiotemporal regions hierarchically for occlusion-free and controllable visual exploration. We enable observation and exploration of the relationships among field line clusters, spatiotemporal regions and their interconnection in the transformed space. Most viewpoint selection methods only consider the external viewpoints outside of the flow field. This will not convey a clear observation when the flow field is clutter on the boundary side. Therefore, we propose a new way to explore flow fields by selecting several internal viewpoints around the flow features inside of the flow field and then generating a B-Spline curve path traversing these viewpoints to provide users with closeup views of the flow field for detailed observation of hidden or occluded internal flow features [54]. This work is also extended to deal with unsteady flow fields. Besides flow field visualization, some other topics relevant to visualization also attract my attention. In iGraph [31], we leverage a distributed system along with a tiled display wall to provide users with high-resolution visual analytics of big image and text collections in real time. Developing pedagogical visualization tools forms my other research focus. Since most cryptography algorithms use sophisticated mathematics, it is difficult for beginners to understand both what the algorithm does and how the algorithm does that. Therefore, we develop a set of visualization tools to provide users with an intuitive way to learn and understand these algorithms.