Sung Kwon Kim

Securing against brute-force attack: A hash-based RFID mutual authentication protocol using a secret value

Radio Frequency IDentification (RFID ) system is a contactless automatic identification system using small, low-cost RFID tags. It enables recognition of the tag information via radio frequency communication, by attaching an RFID tag to an animate or inanimate object. Since an RFID system has the advantage of simultaneously recognizing massive amounts of information, it is expected to replace the bar-code system. The most important problem with an RFID system is that an adversary can access the tag information, which gives rise to privacy and forgery problems. This paper presents a hash-based mutual authentication protocol as a solution. The proposed protocol is designed to send a random number generated by a tag to a back-end server without disclosure. Moreover it substitutes a random number with a secret value, which is employed in a response message. The properties of the proposed protocol enable constant creation of distinct response messages without interferences from intended or meaningless requests generated by an adversary, while the secret value is not directly transmitted. Our proposed protocol make is difficult for an attacker to launch successful brute-force attacks against our approach.

A simple algorithm for the constrained sequence problems

In this paper we address the constrained longest common subsequence problem. Given two sequences X, Y and a constrained sequence P, a sequence Z is a constrained longest common subsequence for X and Y with respect to P if Z is the longest subsequence of X and Y such that P is a subsequence of Z.Recently, Tsai [Inform. Process. Lett. 88 (2003) 173-176] proposed an O(n2 . m2 . r) time algorithm to solve this problem using dynamic programming technique, where n, m and r are the lengths of X, Y and P, respectively.In this paper, we present a simple algorithm to solve the constrained longest common subsequence problem in O(n . m . r) time and show that the constrained longest common subsequence problem is equivalent to a special case of the constrained multiple sequence alignment problem which can also be solved with the same time complexity.

Scalable and flexible privacy protection scheme for RFID systems

Radio Frequency Identification (RFID) system has been studied so much and it may be applicable to various fields. RFID system, however, still has consumer privacy problems under the limitation of low-cost tag implementation. We propose an efficient privacy protection scheme using two hash functions in the tag. We show that our scheme satisfies not only privacy and location history protection of consumers, but also scalability and flexibility of back-end servers. Additionally, we present a practical example to compare performance of several schemes.

RFID Tag Anti-Collision Protocol: Query Tree with Reversed IDs

RFID system is a contactless automatic identification system using small and low-cost RFID tag. It allows to recognize the information of tag via radio frequency attaching RFID tag to an object such as a material object, human or animal. Since RFID system has an advantage to recognize massive information simultaneously, it will be able to replace the bar-code system. For this RFID system to be widely spread, the problem of multiple tag identification, which a reader identifies a multiple number of tags in a very short time, has to be solved. So far, several anti- collision algorithms are developed. We present an RFID tag anti-collision protocol, called the query tree protocol with reversed IDs (QTR protocol). This protocol works by reversing the IDs of the tags and then applying the query tree (QT) protocol. And we present the performances of the QTR protocol by simulation. QTR protocol outperforms QT protocol if the tag IDs are consecutive integers.

Linear-time algorithm for finding a maximum-density segment of a sequence

cien One of the important researches in DNA seque analysis is to find biologically meaningful regions sequences. One such region is a GC-rich region. In GC-rich regions the GC-ratio is much higher than other regions, i.e., the number of the occurrence nucleotidesG or C is significantly larger than tha of nucleotidesA or T . These GC-rich regions ar believed to make a crucial role in recognizing ge related signals in a genome. For example, Ioshik and Zhang [2] and Ohler et al. [4] used GC-ratio one of the parameters in their programs that loc promoter regions in human genome. Related with the application above, Goldwass Kao and Lu [1], and Lin, Jiang and Chao [3] studied abstract optimization problem. (For other applicatio of the problem, see [1,3] and references there To explain the problem we need some definitio and terms. For a sequence A = 〈a1, . . . , an〉 of real numbers, asegment of A is a subsequence 〈ai, . . . , aj 〉

Area-efficient algorithms for straight-line tree drawings

Abstract We investigate several straight-line drawing problems for bounded-degree trees in the integer grid without edge crossings under various types of drawings: (1) upward drawings whose edges are drawn as vertically monotone chains, a sequence of line segments, from a parent to its children, (2) order-preserving drawings which preserve the left-to-right order of the children of each vertex, and (3) orthogonal straight-line drawings in which each edge is represented as a single vertical or horizontal segment. Main contribution of this paper is a unified framework to reduce the upper bound on area for the straight-line drawing problems from O (n log n) (Crescenzi et al., 1992) to O (n loglog n) . This is the first solution of an open problem stated by Garg et al. (1993). We also show that any binary tree admits a small area drawing satisfying any given aspect ratio in the orthogonal straight-line drawing type. Our results are briefly summarized as follows. Let T be a bounded-degree tree with n vertices. Firstly, we show that T admits an upward straight-line drawing with area O (n loglog n) . If T is binary, we can obtain an O (n loglog n) -area upward orthogonal drawing in which each edge is drawn as a chain of at most two orthogonal segments and which has O (n/ log n) bends in total. Secondly, we present O (n loglog n) -area (respectively, -volume) orthogonal straight-line drawing algorithms for binary trees with arbitrary aspect ratios in 2-dimension (respectively, 3-dimension). Finally, we present some experimental results which shows the area requirements, in practice, for (order-preserving) upward drawing are much smaller than theoretical bounds obtained through analysis.

MARP: mobile agent for RFID privacy protection

Recently many researchers in various fields has noticed RFID system. RFID system has many advantages more than other automatic identification system. However, it has some consumer privacy problems, such as location tracking and disclosure of personal information. Most of related works have focused on the cryptographic scheme for the RFID tag and the reader. In this paper, a proxy agent scheme using personal mobile device for the privacy protection. Our MARP, mobile agent for RFID privacy protection, has strong cryptographic modules with a powerful CPU and battery system and guarantees more high-level security than other protection schemes. MARP acquires a tags secrete information partially and becomes the proxy agent of the tag which is in its sleep mode. All readers can communicate with MARP instead of the tag and can attempt authentication with MARP. Since the tag should have only one hash module in the environment of MARP, we can use the existing tag hardware with slight modification for protection consumers privacy in RFID system.

Parallel computational geometry of rectangles

Rectangles in a plane provide a very useful abstraction for a number of problems in diverse fields. In this paper we consider the problem of computing geometric properties of a set of rectangles in the plane. We give parallel algorithms for a number of problems usingn processors wheren is the number of upright rectangles. Specifically, we present algorithms for computing the area, perimeter, eccentricity, and moment of inertia of the region covered by the rectangles inO(logn) time. We also present algorithms for computing the maximum clique and connected components of the rectangles inO(logn) time. Finally, we give algorithms for finding the entire contour of the rectangles and the medial axis representation of a givenn × n binary image inO(n) time. Our results are faster than previous results and optimal (to within a constant factor).

Hybrid Tag Anti-collision Algorithms in RFID Systems

RFID, Radio Frequency Identification, technology is a contactless automatic identification technology about which a lot of researches and developments are recently progressing. For this RFID technology to be widely spread, the problem of multiple tag identification, which a reader identifies a multiple number of tags in a very short time, has to be solved. So far, several anti-collision algorithms are developed. And those can be largely divided into ALOHA based algorithm and tree based algorithm. In this paper, two new anti-collision algorithms combining the characteristics of these two categories are presented. And the performances of the two algorithms are simulated.

Computing the Optimal Bridge between Two Polygons

Abstract. Let P and Q be disjoint polygons in the plane. We consider the problem of finding an optimal bridge (p,q) , p∈ \partial P and q∈ \partial Q , such that the length of the longest path from a point in P , passing through the bridge (p,q) , to a point Q is minimized. We propose efficient algorithms for three cases according to whether P and Q are convex or not. These problems are motivated from the bridge construction between two islands (or the canal construction between two lakes).