Browsing by Author "YANG, WP"

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2D RANDOM FILTER AND ANALYSIS
(1992)
TSENG, JCR
;
YANG, WP
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資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A 2-KEY-LOCK-PAIR ACCESS-CONTROL METHOD USING PRIME FACTORIZATION AND TIME STAMP
(1994-09-01)
HWANG, MS
;
TZENG, WG
;
YANG, WP
;
交大名義發表
;
資訊工程學系
Many methods, based on the concept of key-lock-pair have been proposed for access control in computer protection systems. However, the proposed methods still either lack of dynamic ability or need quite a lot of computation in performing requests of deleting users/files, inserting users/files, or updating access rights of users to files. In this paper we propose a two-key-lock-pair access control method that is based on the unique factorization theorem and a time stamp mechanism. Our method is dynamic and needs a minimum amount of computation in the sense that it only updates at most one key/lock for each access request, which has not been achieved before.
A 2-PHASE ENCRYPTION SCHEME FOR ENHANCING DATABASE-SECURITY
(1995-12-01)
HWANG, MS
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
In this article, we propose a two-phase encryption algorithm for data base systems. The system, a record-oriented cryptosystem, allows the encryption and decryption of fields within a record by means of writing and reading subkeys of fields. In addition, we develop two algorithms for cryptographic relational algebra in data base systems. Two simple methods of solving the key management problem in the subkey scheme are presented.
A BACKTRACKING METHOD FOR CONSTRUCTING PERFECT HASH FUNCTIONS FROM A SET OF MAPPING FUNCTIONS
(1985)
YANG, WP
;
DU, MW
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資訊工程學系
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Department of Computer Science
A NEW DYNAMIC ACCESS-CONTROL SCHEME BASED ON SUBJECT-OBJECT LIST
(1994-11-01)
HWANG, MS
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
The topic of access control modes is a very important subject in the field of information protection systems. In this paper, we shall propose a new access control mode, the subject-object-list (SO-list), for a system which adds, removes, and updates subjects and objects frequently. The main advantage of the SO-list is that the number of lists remains constant despite the changes in the number of subjects/objects. Furthermore, by applying the key-lock-pair mechanism to the list, we allow a new subject/object to be added to or an existing subject/object to be removed from the system without recomputing a large number of key/lock values. Thus, our method achieves real dynamicism.
A NEW DYNAMIC CRYPTOGRAPHIC KEY GENERATION SCHEME FOR A HIERARCHY
(1994)
HWANG, MS
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
A NEW SERVICE FOR DIGITAL MOBILE COMMUNICATIONS
(1994)
HWANG, MS
;
WEY, JK
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
AMORTIZED ANALYSIS OF SOME DISK SCHEDULING ALGORITHMS - SSTF, SCAN, AND N-STEP SCAN
(1992)
CHEN, TS
;
YANG, WP
;
LEE, RCT
;
資訊工程學系
;
Department of Computer Science
The amortized analysis is a useful tool for analyzing the time-complexity of performing a sequence of operations. The disk scheduling problem involves a sequence of requests in general. In this paper, the performances of representative disk scheduling algorithms, SSTF, SCAN, and N-StepSCAN, are analyzed in the amortized sense. A lower bound of the amortized complexity for the disk scheduling problem is also derived. According to our analysis, SCAN is not only better than SSTF and N-StepSCAN, but also an optimal algorithm. Various authors have studied the disk scheduling problem based on some probability models and concluded that the most acceptable performance is obtained from SCAN. Our result therefore supports their conclusion.
AN ENCRYPTION/SIGNATURE SCHEME WITH LOW MESSAGE EXPANSION
(1995-07-01)
HWANG, SJ
;
CHANG, CC
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
Secrecy, authenticity and integrity are three major services provided by the public key cryptography. To provide these three services via the ElGamal public key cryptosystem and Signature scheme, the message expanding ratio is four and the overhead of communication is heavy. In this paper, a concurrent encryption/signature scheme will be proposed to provide these three services with a lower message expanding ratio. In the new scheme, the signer can encrypt and sign the message concurrently so the signature that serves as the ciphertext is a pair of integers. Thus the message expanding ratio can be decreased to two.
ANALYSIS OF THE MULTIGROUP METHOD FOR MANIPULATING MULTIPLE STACKS
(1993-02-01)
CHIEN, BC
;
CHEN, RJ
;
YANG, WP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The multiple stacks problem is that a number of stacks have to be manipulated in a finite continuous memory, simultaneously. Many applications need the support of multiple stacks, e.g., the parallel computing with shared memory. There are two approaches mentioned in [1] for manipulating multiple stacks. In this paper, we present and analyze the Multigroup method which combines the concept of coexisting. By the concept of coexisting, storage sharing in a linear data structure is possible. We show that the new method has better performance than the two previous approaches, and improves the extra manipulating time.
ANSWERING HETEROGENEOUS DATABASE QUERIES WITH DEGREES OF UNCERTAINTY
(1993-07-01)
TSENG, FSC
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CHEN, ALP
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YANG, WP
;
資訊工程學系
;
Department of Computer Science
In heterogeneous database systems, partial values have been used to resolve some schema integration problems. Performing operations on partial values may produce maybe tuples in the query result which cannot be compared. Thus, users have no way to distinguish which maybe tuple is the most possible answer. In this paper, the concept of partial values is generalized to probabilistic partial values. We propose an approach to resolve the schema integration problems using probabilistic partial values and develop a full set of extended relational operators for manipulating relations containing probabilistic partial values. With this approach, the uncertain answer tuples of a query are associated with degrees of uncertainty (represented by probabilities). That provides users a comparison among maybe tuples and a better understanding on the query results. Besides, extended selection and join are generalized to alpha-selection and alpha-join, respectively, which can be used to filter out maybe tuples with low probabilities-those which have probabilities smaller than alpha.
BROADCASTING ON INCOMPLETE HYPERCUBES
(1993-11-01)
TIEN, JY
;
HO, CT
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YANG, WP
;
資訊工程學系
;
Department of Computer Science
Incomplete hypercubes make the hypercubes more flexible on task allocation in large cubes, cost of manufacturing hardware, and hypercubes with faulty nodes. In this correspondence, we devise and analyze a broadcasting algorithm based on edge-disjoint spanning trees in an incomplete hypercube of 2n + 2k nodes, where 0 less-than-or-equal-to k less-than-or-equal-to n. The broadcasting algorithm is strictly optimal.
COMPETITIVE ANALYSIS OF THE ONLINE ALGORITHMS FOR MULTIPLE STACKS SYSTEMS
(1992-01-01)
CHIEN, BC
;
CHEN, RJ
;
YANG, WP
;
資訊工程學系
;
資訊科學與工程研究所
An on-line problem is one in which an algorithm must handle a sequence of requests, satisfying each request without knowledge of the future requests. A competitive algorithm is an on-line algorithm whose cost is bounded by the cost of any other algorithm, even the algorithm is an optimal off-line algorithm, multipling a constant. This paper discusses the algorithms used to manipulate the multiple stacks problem, which is one of the on-line problems. We find the optimal off-line algorithm first, then show that the Knuth's algorithm is not a competitive algorithm, but Garwick's algorithm is competitive when the number Of stacks n is 2. Furthermore the competitive ratio found here is a low bound if the Garwick's algorithm is also & competitive algorithm for n greater-than-or-equal-to 3.
COMPETITIVE ANALYSIS OF THE ONLINE ALGORITHMS FOR MULTIPLE STACKS SYSTEMS
(1992)
CHIEN, BC
;
CHEN, RJ
;
YANG, WP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
An on-line problem is one in which an algorithm must handle a sequence of requests, satisfying each request without knowledge of the future requests. A competitive algorithm is an on-line algorithm whose cost is bounded by the cost of any other algorithm, even the algorithm is an optimal off-line algorithm, multipling a constant. This paper discusses the algorithms used to manipulate the multiple stacks problem, which is one of the on-line problems. We find the optimal off-line algorithm first, then show that the Knuth's algorithm is not a competitive algorithm, but Garwick's algorithm is competitive when the number Of stacks n is 2. Furthermore the competitive ratio found here is a low bound if the Garwick's algorithm is also & competitive algorithm for n greater-than-or-equal-to 3.
CONCURRENT OPERATIONS IN LINEAR HASHING
(1990-07-01)
HSU, MC
;
TUNG, SS
;
YANG, WP
;
交大名義發表
;
National Chiao Tung University
CONCURRENT OPERATIONS IN MULTIATTRIBUTE LINEAR HASHING
(1993-10-15)
HO, PC
;
YANG, WP
;
HSU, MC
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Linear hashing is a dynamic hash structure in which the address space may vary dynamically when the database size is changed. Multi-attribute linear hasing is a generalization of linear hashing. It supports operations for associative search and may have wider applicability. This paper presents an algorithm for synchronizing concurrent operations in multi-attribute linear hashing with particular attention paid to the treatment of concurrent partial-match operations. Unlike the previous non-two-phase methods, the algorithm employs the principle of optimistic concurrency control technique, which leads an operation to ''retry'' when interference from concurrent conflicting operations occurs. The method also uses a strictly increasing counter to filter out a significant number of unnecessary retries, thus allowing search, partial-match, insert, and delete operations to proceed concurrently with split and merge operations. The search and partial-match operations do not need to set any lock, and no operations need to set locks on any shared global variables. Therefore, the operations potentially allow a higher degree of concurrency in the system. An argument for the correctness based on the notions of weak consistency and a discussion for the performance of the proposed algorithm are also present.
CONFERENCE KEY DISTRIBUTION SCHEMES FOR SECURE DIGITAL MOBILE COMMUNICATIONS
(1995-02-01)
HWANG, MS
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a new service for digital mobile communication systems, The service enables two or more users to hold a secure conference, Two requirements must be considered: privacy and authentication. Privacy involves ensuring that an eavesdropper cannot intercept the conversations of the parties holding the conference. Authentication involves ensuring that service is not obtained fraudulently in order to avoid usage charges. We present two new conference key distribution schemes for digital mobile communication systems. In these schemes, a group of users can generate a common secret key over a public channel so that they may hold a secure conference.
EQL: A learn-easy and use-easy query language for object-oriented databases
(1995)
PAN, WW
;
YANG, WP
;
資訊工程學系
;
Department of Computer Science
FINDING A COMPLETE MATCHING WITH THE MAXIMUM PRODUCT ON WEIGHTED BIPARTITE GRAPHS
(1993-03-01)
TSENG, FSC
;
YANG, WP
;
CHEN, ALP
;
資訊工程學系
;
Department of Computer Science
The traditional bipartite weighted matching problem is to maximize the largest possible sum of weights. In this paper, we define a bipartite matching problem which maximizes the largest possible product of weights and develop an algorithm to solve it. Although this problem corresponds to a non-linear program, we show this problem can be easily solved by modifying the Hungarian method. Finally, we present an application of this problem.
HIERARCHICAL SPANNING-TREES AND DISTRIBUTING ON INCOMPLETE HYPERCUBES
(1991-12-01)
TIEN, JY
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YANG, WP
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資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Incomplete hypercubes are gaining increasing attention as one of the possible solutions for the limitation on the number of nodes in the hypercubes. Distributing, in which one node sends distinct messages to distinct nodes, and its reverse operation are frequently used operations on data parallel computation. In this paper, we propose two types of spanning trees in incomplete hypercubes (composed of an n-cube and a k-cube): the binomial hierarchical spanning tree-binomial HST, and the balanced hierarchical spanning tree-balanced HST, for distributing (and its reverse operation). Distributing algorithms based on a balanced HST take better advantage of overlap between communication ports, or have speedup up to k/2 or n/2 over that based on the binomial HST when concurrently communication on all ports are possible, from the view point of communication complexity. An algorithm to construct hierarchical spanning trees in general incomplete hypercubes, which consist of an arbitrary number of nodes, is also devised.