Fundamenta Informaticae - Volume 76, issue 4

Authors: Chang, Chin-Chen | Lin, Chih-Yang | Tseng, Chun-Sen

Article Type: Research Article

Abstract: This study proposes a new secret image sharing method based on the (t,n)-threshold. The sharing method is completed through three main steps: (1) quantizing the secret image, (2) generating n shadows from the quantized image, and (3) sharing the n shadows among n cover images. Our goal is both to attain good stego-image and secret image quality preservation effects and to limit the size of each shadow image down to 1/t of that of the secret image for …convenient transmission and storage. In the first step, the secret image is divided into non-overlapping 4 × 4 blocks that are quantized according to the results of block testing. Each block, after the block testing procedure, is judged to be either a smooth block or a non-smooth one. Smooth blocks can be neatly restored after being hidden into the cover image, while non-smooth blocks can be somewhat lossy, but such modification is perceptually invisible. The second step is to apply Shamir's (t,n)-threshold, which uses a (t−1)-degree polynomial to generate n shadows so that the secret image can be restored from any t out of n shadows. The last step involves a modulo operation to hide the n shadows in n cover images. According to our experimental results, the PSNR values of the reconstructed secret images by our method center around 39 dB, outperforming other recent methods. Show more

Keywords: Secret image sharing, steganography, image quantization, (t,n)-threshold secret sharing

Citation: Fundamenta Informaticae, vol. 76, no. 4, pp. 399-411, 2007

Authors: Konstantinidis, Stavros | Nicolae, Santean | Yu, Sheng

Article Type: Research Article

Abstract: In this paper we present a different framework for the study of fuzzy finite machines and their fuzzy languages. Unlike the previous work on fuzzy languages, characterized by fuzzification at the level of their acceptors/generators, here we follow a top-down approach by starting our fuzzification with more abstract entities: monoids and particular families in monoids. Moreover, we replace the unit interval (in fact, a finite subset of the unit interval) as support for fuzzy values with …the more general structure of a lattice. We have found that completely distributive complete lattices allow the fuzzification at the highest level, that of recognizable and rational sets. Quite surprisingly, the fuzzification process has not followed thoroughly the classical (crisp) theory. Unlike the case of rational sets, the fuzzification of recognizable sets has revealed a few remarkable exceptions from the crisp theory: for example the difficulty of proving closure properties with respect to complement, meet and inverse morphisms. Nevertheless, we succeeded to prove the McKnight and Kleene theorems for fuzzy sets by making the link between fuzzy rational/recognizable sets on the one hand and fuzzy regular languages and FT-NFA languages (languages defined by NFA with fuzzy transitions) on the other. Finally, we have drawn the attention to fuzzy rational transductions, which have not been studied extensively and which bring in a strong note of applicability. Show more

Keywords: Fuzzy Transducer, Rational Set, Recognizable Set, Lattice

Citation: Fundamenta Informaticae, vol. 76, no. 4, pp. 413-447, 2007

Authors: Peltier, Nicolas

Article Type: Research Article

Abstract: We present a resolution calculus for first-order logic using a more concise formalism for representing sets of clauses. The idea is to represent the clause set at hand as a Directed Acyclic Graph, which allows one to share common literals instead of duplicating them, thus yielding a much more compact representation of the search space. We define inference rules operating on this language and we prove their soundness and refutational completeness. We also design simplification rules …for pruning the search space. Finally we compare our technique with the usual resolution calculus and we prove (using the pigeonhole example) that our method can reduce the length of the proof by an exponential factor (in propositional logic). Show more

Keywords: Resolution, Sharing, Pigeonhole problem

Citation: Fundamenta Informaticae, vol. 76, no. 4, pp. 449-480, 2007

Authors: Wu, Hsien-Chu | Chang, Chin-Chen

Article Type: Research Article

Abstract: This paper proposes two kinds of image features. One feature is the spatial-histogram feature. It combines the color histogram feature and the information about the dimensional position of pixels in an image to record the distribution of the pixels' colors that are present in different spatial positions within an image. The other image feature proposed in this paper is the color-complexity feature, which can be used to describe the change of pixel colors in the image. …From the experimental results, ANMRR value is provided and we observe that the image retrieval system based on these two kinds of image features can provide a fairly good accuracy rate in image retrieval. Moreover, it has the capacity to tolerate errors; that is, for images that are damaged by rotation, shift, or color variant attacks, their similar image pairs can still be retrieved from the image database. Thus, the accuracy and flexibility of the image retrieval system are drastically improved. Show more

Keywords: Color-based image retrieval, color complexity, color histogram, K-mean

Citation: Fundamenta Informaticae, vol. 76, no. 4, pp. 481-493, 2007

Authors: Ziembiński, Radosław

Article Type: Research Article

Abstract: This paper describes practical aspects of a novel approach to the sequential pattern mining named Context Based Sequential Pattern Mining (CBSPM). It introduces a novel ContextMapping algorithm used for the context pattern mining and an illustrative example showing some advantages of the proposed method. The approach presented here takes into consideration some shortcomings of the classic problem of the sequential pattern mining. The significant advantage of the classic sequential patterns mining is simplicity. …It introduces simple element construction, built upon set of atomic items. The comparison of sequence's elements utilizes simple inclusion of sets. But many practical problems like web event mining, monitoring, tracking and rules generation often require mining more complex data. The CBSPM takes into account non nominal attributes and similarity of sequence's elements. An approach described here extends traditional problem adding a vector of context attributes of any kind to sequences and sequences elements. Context vectors contain details about sequence's and element's origin. The mining process results in context patterns containing additional, valuable context information useful in interpretation of patterns origin. Show more

Keywords: knowledge discovery, sequential patterns mining, events mining, patterns, context patterns, context mapping

Citation: Fundamenta Informaticae, vol. 76, no. 4, pp. 495-510, 2007