arXiv subjects

Pino Caballero-Gil

Publications and source records attributed to Pino Caballero-Gil.

26 records · Page 2Linked to original sources

arXiv2022

Weak Equivalents for Nonlinear Filtering Functions

The application of a nonlinear filtering function to a Linear Feedback Shift Register (LFSR) is a general technique for designing pseudorandom sequence generators with cryptographic application. In this paper, we investigate the equivalence between different nonlinear filtering functions applied to distinct LFSRs. It is a well known fact that given a binary sequence generated from a pair (nonlinear filtering function, LFSR), the same sequence can be generated from any other LFSR of the same length by using another filtering function. However, until now no solution has been found for the problem of computing such an equivalent. This paper analyzes the specific case in which the reciprocal LFSR of a given register is used to generate an equivalent of the original nonlinear filtering function. The main advantage of the contribution is that weaker equivalents can be computed for any nonlinear filter, in the sense that such equivalents could be used to cryptanalyze apparently secure generators. Consequently, to evaluate the cryptographic resistance of a sequence generator, the weakest equivalent cipher should be determined and not only a particular instance.

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arXiv2022

Analysis of lightweight cryptographic solutions for authentication in IoT

Currently, special attention is being paid to scenarios where the interconnection of devices with heterogeneous computational and communication capabilities it is required. It is essential to integrate security services during the stages of design and deployment of these networks since many of these scenarios provide critical services such as medical health, payment systems, military affairs, access control, e-banking, etc. This work analyses several cryptographic primitives related to entity authentication providing robust solutions according to device capabilities.

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arXiv2022

Strong authentication on smart wireless devices

The rapid deployment of wireless technologies has given rise to the current situation where mobile phones and other wireless devices have become essential elements in all types of activities, including in the home. In particular, smartphones and laptops are used for wirelessly sharing photos and documents, playing games, browsing websites, and viewing multimedia, for example. This work describes a proposal for both desktop and mobile applications that use Identity-Based Cryptography (IBC) to protect communications between smart wireless devices in the home. It combines the use of IBC for Wi-Fi and Bluetooth communication, with the promising Near Field Communication (NFC) technology for secure authentication. The proposed scheme involves NFC pairing to establish as public key a piece of information linked to the device, such as a phone number or an IP address. In this way, such information can be then used in an IBC scheme for peer-to-peer communication. This is a work in progress, but preliminary implementations of prototypes on several mobile platforms have already produced promising results.

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arXiv2022

Using query frequencies in tree-based revocation for certificateless authentication in VANETs

Revocation of dishonest users is not an easy problem. This paper proposes a new way to manage revocation of pseudonyms in vehicular ad-hoc networks when using identity-based authentication to increase efficiency and security through certificateless authentication. In order to improve the performance of revocation lists, this paper proposes the use of a data structure based on authenticated dynamic hash k-ary trees and the frequency with which revoked pseudonyms are consulted. The use of the knowledge about the frequency of consultation of revoked pseudonyms allows an easier access to the most popular revoked pseudonyms to the detriment of revoked pseudonyms that are the least consulted. Accordingly, the proposal is especially useful in urban environments where there are vehicles that spend more time on road than others, such as public service vehicles.

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arXiv2010

On the Use of Cellular Automata in Symmetric Cryptography

In this work, pseudorandom sequence generators based on finite fields have been analyzed from the point of view of their cryptographic application. In fact, a class of nonlinear sequence generators has been modelled in terms of linear cellular automata. The algorithm that converts the given generator into a linear model based on automata is very simple and is based on the concatenation of a basic structure. Once the generator has been linearized, a cryptanalytic attack that exploits the weaknesses of such a model has been developed. Linear cellular structures easily model sequence generators with application in stream cipher cryptography.

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arXiv2010

Linear Cellular Automata as Discrete Models for Generating Cryptographic Sequences

In this paper, we develop a new cellular automata-based linear model for several nonlinear pseudorandom number generators with practical applications in symmetric cryptography. Such a model generates all the solutions of linear binary difference equations as well as many of these solutions are pseudo-random keystream sequences. In this way, a linear structure based on cellular automata may be used to generate not only difference equation solutions but also cryptographic sequences. The proposed model is very simple since it is based exclusively on successive concatenations of a basic linear automaton.

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arXiv2010

New Attack Strategy for the Shrinking Generator

This work shows that the cryptanalysis of the shrinking generator requires fewer intercepted bits than what indicated by the linear complexity. Indeed, whereas the linear complexity of shrunken sequences is between $A \cdot 2^(S-2)$ and $A \cdot 2^(S-1)$, we claim that the initial states of both component registers are easily computed with less than $A \cdot S$ shrunken bits. Such a result is proven thanks to the definition of shrunken sequences as interleaved sequences. Consequently, it is conjectured that this statement can be extended to all interleaved sequences. Furthermore, this paper confirms that certain bits of the interleaved sequences have a greater strategic importance than others, which may be considered as a proof of weakness of interleaved generators.

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arXiv2010

On the Design of Cryptographic Primitives

The main objective of this work is twofold. On the one hand, it gives a brief overview of the area of two-party cryptographic protocols. On the other hand, it proposes new schemes and guidelines for improving the practice of robust protocol design. In order to achieve such a double goal, a tour through the descriptions of the two main cryptographic primitives is carried out. Within this survey, some of the most representative algorithms based on the Theory of Finite Fields are provided and new general schemes and specific algorithms based on Graph Theory are proposed.

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