Catálogo de publicaciones - libros

This paper presents a non-committing encryption scheme based on quadratic residue. It is a solution to adaptive security of multiparty computation with non-erasing parties in the cryptographic model. The scheme is more efficient than all previous non-committing encryption schemes. Furthermore, we give security proofs.

Biometric cryptosystems combine cryptography and biometrics to benefit from the strengths of both fields. In such systems, while cryptography provides high and adjustable security levels, biometrics brings in non-repudiation and eliminates the need to remember passwords or to carry tokens etc. In this work, we present a biometric cryptosystem which uses online signatures, based on the fuzzy vault scheme of Jules et al. The fuzzy vault scheme releases a previously stored key when the biometric data presented for verification matches the previously stored template hidden in a vault. The online signature of a person is a behavioral biometric which is widely accepted as the formal way of approving documents, bank transactions, etc. As such, biometric-based key release using online signatures may have many application areas.

We extract minutiae points (trajectory crossings, endings and points of high curvature) from online signatures and use those during the locking & unlocking phases of the vault. We present our preliminary results and demonstrate that high security level (128 bit encryption key length) can be achieved using online signatures.

We introduce an efficient method for computing Montgomery products of polynomials in the frequency domain . The discrete Fourier transform (DFT) based method originally proposed for integer multiplication provides an extremely efficient method with the best asymptotic complexity, i.e. O ( m log m loglog m ), for multiplication of m -bit integers or ( m –1)^ st degree polynomials. However, the original DFT method bears significant overhead due to the conversions between the time and the frequency domains which makes it impractical for short operands as used in many applications. In this work, we introduce DFT modular multiplication which performs the entire modular multiplication (including the reduction step) in the frequency domain, and thus eliminates costly back and forth conversions. We show that, especially in computationally constrained platforms, multiplication of finite field elements may be achieved more efficiently in the frequency domain than in the time domain for operand sizes relevant to elliptic curve cryptography (ECC). To the best of our knowledge, this is the first work that proposes the use of frequency domain arithmetic for ECC and shows that it can be efficient.

In 2004, Shao pointed out that both Sun et al.’s and Hsu et al.’s threshold proxy signature schemes are vulnerable to coalition attack. For enhancing the security, Shao proposed an improved scheme with anonymity to outsiders. This signature scheme is meaningless to any outsider because there is no way for him to prove each individual proxy signing public key validity. We further propose a practical threshold proxy signature scheme to remedy this drawback. The new scheme has the following advantages: (l) Any verifier can check whether the authors of the proxy signature belong to the designated proxy group by the original signer, while outsiders cannot find the actual signers; (2) The original signer can identify the actual proxy signers; (3) The verification of the proxy signing public keys of the proxy signers and the threshold proxy signature can be accomplished within a signature verification procedure simultaneously.

An efficient algorithm to compute the degree of balancedness in LFSR-based sequence generators has been developed. The computation is realized by means of logic operations on bit-strings. Emphasis is on the computational features of this algorithm. The procedure checks deviation of balancedness from standard values for this type of generators with application in symmetric cryptography.

A test suite, constructed either manually or automatically using a coverage criterion, can be reduced without significantly reducing its fault-detection capability by eliminating all but one of the equivalent test cases from each class of equivalent test cases of the test suite. In this paper, we use the analysis of control and data dependencies in an EFSM model of the system requirements to identify patterns of interaction among the elements of the EFSM that affect a requirement under test. These patterns are used to identify equivalent test cases w.r.t. the requirement under test; only one test case per equivalence class is kept, and equivalence classes that are not covered by any test cases are flagged. A software tool – Test Suite Reduction (TSR) based on above concept- is introduced. This tool is implemented in C++ and Java languages and runs on Sun workstations under Solaris Sparc 5.8. Additionally, the results of the application of TSR to several examples are also presented.

A software engineering course is often the capstone of a general undergraduate curriculum in computer science. It is usually at least partly a project-based course, with the intention that student groups can deploy their already acquired skills on programming, verification, databases, and human-computer interaction, while applying the new material about requirements, architecture, and project management on a project. I have taught a software engineering course six times, using a combination of ideas that I have never seen elsewhere, with a strong emphasis on realism. I here reflect on the rewards and risks of this approach, and make some recommendations for future offerings.

Although several quantum programming languages have already been proposed, none of these are based on the newly discovered adiabatic evolution approach. We examine some flow control constructs like loops and branching from the adiabatic quantum perspective to illustrate the main design problems as a first step towards the development of an adiabatic quantum programming infrastructure.

In cognitive functional size measure, the functional size is proportional to weighted cognitive complexity of all internal BCS‘s and number of input and output. This paper proposes the modification in cognitive functional size complexity measure. The proposed complexity measure is proportional to total occurrence of operators and operands and all internal BCS´s. The operators and operands are equally important in design consideration. Thus, the contribution of the operators, operands and cognitive aspects complete the definition of a complexity measure in terms of cognitive. Accordingly, a new formula is developed for calculating the modified cognitive complexity measure. An attempt has also been made to evaluate modified cognitive complexity measure in terms of nine Weyuker’s properties, through examples. It has been found that seven of nine Weyuker’s properties have been satisfied by the modified cognitive complexity measure and hence establishes as a well-structured one.

Graph-based algorithms are commonly used to automatically gener ate test cases for coverage-oriented testing of software systems. Because of time and cost constraints, the entire set of test cases generated by those algorithms cannot be run. It is then essential to prioritize the test cases in sense of a rank ing, i.e., to order them according to their significance which usually is given by several attributes of relevant events entailed. This paper suggests unsupervised neural network clustering of test cases for forming preference groups, where adaptive competitive learning algorithm is applied for training the neural net work used. A case study demonstrates and validates the approach.