Oscar Delgado-Mohatar

A light-weight authentication scheme for wireless sensor networks

Sensor networks are ad hoc mobile networks that include sensor nodes with limited computational and communication capabilities. They have become an economically viable monitoring solution for a wide variety of applications. Obviously, security threats need to be addressed and, taking into account its limited resources, the use of symmetric cryptography is strongly recommended. In this paper, a light-weight authentication model for wireless sensor networks composed of a key management and an authentication protocol is presented. It is based on the use of simple symmetric cryptographic primitives with very low computational requirements, which obtains better results than other proposals in the literature. Compared to SPINS and BROSK protocols, the proposal can reduce energy consumption by up to 98% and 67%, respectively. It also scales well with the size of the network, due to it only requiring one interchanged message, independently of the total number of nodes in the network.

Deterministic Computation of Pseudorandomness in Sequences of Cryptographic Application

An easy method of checking balancedness degree as well as run quantification in sequences obtained from LFSR-based keystream generators has been developed. The procedure is a deterministic alternative to the traditional application of statistical tests. The computation method allows one to check deviation of balancedness and run distribution goodness from standard values. The method here developed can be considered as a first selective criterium for acceptance/rejection of this type of generators of cryptographic application.

An energy-efficient symmetric cryptography based authentication scheme for wireless sensor networks

Sensor networks are ad-hoc mobile networks that include sensor nodes with limited computational and communication capabilities. They have become an economically viable monitoring solution for a wide variety of applications. Obviously, it is important to ensure security and, taking into account limited resources available in wireless sensor networks, the use of symmetric cryptography is strongly recommended. In this paper we present a light-weight authentication model for wireless sensor networks composed of a key management and an authentication protocol. It is based on simple symmetric cryptographic primitives with very low computational requirements, and it achieves better results than other similar proposals in the literature. Compared to SPINS and BROSK protocols, our system can reduce energy consumption by up to 98% and 67% respectively. It also scales well with the size of the network, due to it only requiring one interchanged message, regardless of the total number of nodes in the network.

Software Implementation of Linear Feedback Shift Registers over Extended Fields

Linear Feedback Shift Registers are currently used as generators of pseudorandom sequences with multiple applications from communication systems to cryptography. In this work, design and software implementation of LFSRs defined over extended fields GF(2 n ) instead of over the binary field GF(2) are analyzed. The key idea is to take profit of the underlying structure of the processor over which the application is executed. The study has been carried out for diverse extended fields and different architectures. Numerical results prove that extended fields provide speedup factors up to 10.15. The benefits of these fields are clear for LFSR applications included cryptographic applications.

On the linearity of cryptographic sequence generators

In this paper we show that the output sequences of the generalized self-shrinking generator are particular solutions of a binary homogeneous linear difference equation. In fact, all these sequences are just linear combinations of primary sequences weighted by binary coefficients. We show that in addition to the output sequences of the generalized self-shrinking generator, the complete class of solutions of the corresponding binary homogeneous linear difference equation also includes other balanced sequences that are very suitable for cryptographic applications, as they have the same period and even greater linear complexity than the generalized self-shrinking sequences. Cryptographic parameters of all the above mentioned sequences can be analyzed in terms of linear equation solutions.

Performance evaluation of highly efficient techniques for software implementation of LFSR

Linear feedback shift registers (LFSR) are widely used in many different areas. In this paper, we study the operation of LFSR defined over extension fields GF(2^n), instead of traditional binary fields, quantifying and comparing the theoretical with the real performance improvement. We also examine other techniques for efficient implementation, analyzing the effectiveness of both approaches. The experiments show that speedups up to 10.15 can be easily achieved. Surprisingly, data also show that the use of extension fields greater than GF(2^1^6) is not always worth, due to the increasing internal operation costs. The benefits are clear for all possible applications of LFSR, and specifically for cryptographic purposes.

Testing Topologies for the Evaluation of IPSEC Implementations

The use of virtual private networks (VPNs) for the communications protection is becoming increasingly common. Likewise, the IPSEC architecture has been gaining ground and, at present, is the solution more used for this purpose. That is the reason why a large number of implementations of IPSEC have been created and put into operation. This work proposes three testing topologies to carry out IPSEC implementation assessment, each of these scenarios will supply an important guide for the determination of objectives, digital evidences to collect and test batteries to develop, in any evaluation of a IPSEC device.

Design of Decimation-Based Sequence Generators over Extended Fields

Linear Feedback Shift Registers are currently used as generators of pseudorandom sequences with application in many and different areas. In this work, analysis and software implementation of LFSRs defined over extended fields GF(2n) (where n is related to the size of the registers in the underlying processor) instead of over the binary field GF(2) have been considered. Once the migration from GF(2) into GF(2n) has been accomplished, a study of decimation-based sequence generators has been proposed. Definition of new decimation criteria as well as their software implementation and corresponding analysis complete the work.

Using New Tools for Certificate Repositories Generation in MANETs

This paper includes a new proposal for the generation of certificates repositories in MANETs. The described process is based on the combination of the self-organized key management model together with the MultiPoint Relay (MPR) technique, generally used in the Optimized Link State Routing protocol. The main objective is to reduce the cost of generating and updating local certificate repositories by selecting those certificates that allow to reach the maximum number of nodes. This goal is just achieved by applying low-cost operations carried out locally by the nodes themselves.