Browsing by Author "WU, TC"

Now showing 1 - 14 of 14

A CONFERENCE KEY DISTRIBUTION-SYSTEM BASED ON CROSS-PRODUCT
(1993-02-01)
WU, TC
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YEH, YS
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交大名義發表
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資訊科學與工程研究所
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National Chiao Tung University
Extended from the Diffie-Hellman public key distribution system (PKDS), we propose a conference key distribution system (CKDS) based on the cross-product operations on row vectors over a Galois field GF(P), where P is a prime number. In our CKDS, the chairperson computes a conference key CK and then embeds it to some public interpolating polynomials to let only the legal intended principals recover CK, while the illegal intended principals can not. From the public parameters, an intruder or any intended principal in the network does not know how many and who are the legal intended principals in the conference. Furthermore, since the construction of the CK does not interfere with the secret keys of the intended principals, any intended principals in the network has no useful information for revealing any other principals' secret keys. Besides, our CKDS can be implemented practically.
A LETTER-ORIENTED PERFECT HASHING SCHEME BASED UPON SPARSE TABLE COMPRESSION
(1991-01-01)
CHANG, CC
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WU, TC
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
In this paper, a new letter-oriented perfect hashing scheme based on Ziegler's row displacement method is presented. A unique n-tuple from a given set of static letter-oriented key words can be extracted by a heuristic algorithm. Then the extracted distinct n-tuples are associated with a 0/1 sparse matrix. Using a sparse matrix compression technique, a perfect hashing function on the key words is then constructed.
A PASSWORD AUTHENTICATION SCHEME BASED ON DISCRETE LOGARITHMS
(1991)
WU, TC
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CHANG, CC
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
ALGEBRAIC OPERATIONS ON ENCRYPTED RELATIONAL DATABASES
(1993-01-01)
WU, TC
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YEH, YS
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CHANG, CC
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資訊科學與工程研究所
;
Institute of Computer Science and Engineering
In this paper, we consider the problem of performing algebraic operations and their extensions with encrypted relational databases. Each tuple of a relation is enciphered by a cryptosystem based on the extended Chinese remainder theorem. We show that one can perform the Projection, the Cartesian Product and their composite operations, such as performing the Projection followed by the Cartesian Product and performing Cartesian Product followed by the Projection, with the encrypted tuples directly without deciphering them. We also show that there does not exist a secure way to protect data for performing Comparison operations, such as Selection, Union,... , etc., with encrypted relational databases.
ALGORITHMS FOR THE RURAL POSTMAN PROBLEM
(1995-10-01)
PEARN, WL
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WU, TC
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工業工程與管理學系
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Department of Industrial Engineering and Management
The rural postman problem (RPP) is a practical extension of the well-known Chinese postman problem (CPP), in which a subset of the edges (streets) from the road network are required to be traversed at a minimal cost. The RPP is NP-complete if this subset does not form a weakly connected network. Therefore, it is unlikely that polynomial-time bounded algorithms exist for the problem. In this paper, we review the existing heuristic solution procedures, then present two new algorithms to solve the problem near-optimally. Computational results showed that the proposed new algorithms significantly outperformed the existing solution procedures.
AN AUTHENTICATION-COMBINED ACCESS-CONTROL SCHEME USING A ONE-WAY FUNCTION
(1994-03-01)
WU, TC
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CHANG, CC
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YEH, YS
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
In this paper, we propose an authentication-combined access control scheme for information protection systems. Let a(ij) be the access privilege of User i to File j. Initially, by the Diffie-Hellman public key distribution scheme, the system and the users are assigned distinct secret keys, and their corresponding public keys, respectively. Let K(s) be the secret key and y(s) be the public key of the system, and let K(i) be the secret key and y(i) be the public key of the User i. By using a predefined one-way function F, we compute r(ij) = F(K(i), y(s), a(ij)). Reversely, the access privilege can be retained as a(ij) = F(K(s), y(i), r(ij)). Being different from the previously proposed schemes, our scheme is safer and the user's secret key is used not only for computing the corresponding access privilege to the intended file, but also for authenticating the requesting user not to illegitimately access the protected files. The proposed scheme is simple to establish. Besides, it can perform the access control in dynamic environments, such as change access privileges and insert/delete users or files.
BROADCASTING CRYPTOSYSTEM IN COMPUTER-NETWORKS USING INTERPOLATING POLYNOMIALS
(1991-07-01)
CHANG, CC
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WU, TC
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
Based on the characteristics of the interpolating polynomials and some properties of the Euclidean geometry, a cryptosystem for broadcasting secrets in computer networks is presented. It is assumed that there is a central authority server (CAS) in a network system. Each principal of the network owns a secret point, known only to the principal and the CAS. When a secure broadcasting request is initiated, the CAS computes an interpolating polynomial P(x) on the secret points owned by the originator and the legal recipient(s). The CAS then cleverly reveals some public points to let the originator and legal recipient(s) reconstruct P(x), whereas illegal recipients are unable to do so. With these public points and a value c, the originator has P(c) as the encryption/decryption key, and can broadcast c and the message encrypted by P(c) in the network. For the legal recipients, P(x) can be reconstructed, and thus P(c) obtained. Since the legal recipients cannot obtain the exact P(x), they have no way of finding the decryption key.
COLOR IMAGE SHARPENING BY MOMENT-PRESERVING TECHNIQUE
(1995-09-01)
YANG, CK
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WU, TC
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LIN, JC
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TSAI, WH
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資訊工程學系
A new approach to sharpening color images using the moment-preserving technique is proposed, An input image is processed pixel by pixel. By preserving some color moments of the n x n neighborhood of each pixel, analytic formulas are derived to compute two sets of (R, G, B) tristimulus values, and one of them is assigned to the pixel as the sharpening result. Cases with one or more uniform color components in the neighborhood are also treated. The proposed method preserves spatial details, and requires little memory and small computational load, The proposed sharpening operation can also be applied iteratively to the input image to get better sharpening effect. Experimental results show that the proposed approach is effective for color image sharpening.
CONTROLLING THE ACCESS REQUESTS IN AN INFORMATION PROTECTION SYSTEM
(1993-01-01)
CHANG, CC
;
WU, TC
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資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A new mechanism used for controlling the access requests in information systems is proposed. In our scheme, each access privilege associates to a recursively generated function based on Newton's interpolating polynomial. The insertion of a new user/file into the system and deletion of an old user/file from the system can be easily implemented. Besides, the updating of a privilege of a user to a file can also be successfully implemented without reconstructing all associated functions.
CRYPTOGRAPHIC KEY ASSIGNMENT SCHEME FOR ACCESS-CONTROL IN A HIERARCHY
(1992-05-01)
CHANG, CC
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HWANG, RJ
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WU, TC
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資訊工程學系
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Department of Computer Science
A cryptographic key assignment scheme for access control in a user hierarchy is proposed. The users and their owned information items are classified into disjoint sets of security classes where the hierarchy on security classes is an arbitrary partial order. Based on Newton's interpolation method and a predefined one-way function, each security class C(i) is assigned a secret key SK(i) and some public parameters (P1i, P2i). The information items owned by the security class C(i) are encrypted by an available symmetric cryptosystem with the enciphering key SK(i). Through the computing of the assigned security key and the public parameters, only the security class in the higher level can derive any of his successors' secret keys. Thus, only the security classes in the higher level can access the information items owned by the security classes in the lower level. We also show that our proposed scheme is not only secure but also practical.
CRYPTOSYSTEM FOR SELECTIVELY BROADCASTING SEPARATE SECRETS
(1993-04-01)
WU, TC
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YEH, YS
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
PASSWORD AUTHENTICATION USING NEWTON INTERPOLATING POLYNOMIALS
(1991)
LIN, CH
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CHANG, CC
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WU, TC
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LEE, RCT
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資訊科學與工程研究所
A password authentication mechanism based upon Newton's interpolating polynomial and a strong cryptographic operation such as DES (data encryption standard) is proposed in this paper. The mechanism can respond to any login request very efficiently. It is suitable for real-time applications and can be implemented in microcomputer system. With the properties of Newton's interpolating polynomial, high system performance can be achieved. The basic idea of our method is that users in the system are congregated together. Any illegal modification by an intruder to some user's parameter on the host tables will influence the others and can be easily detected. However, legitimate modification of password could be made efficiently.
REMOTE PASSWORD AUTHENTICATION WITH SMART CARDS
(1991-05-01)
CHANG, CC
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WU, TC
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資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A remote password authentication scheme based on the Chinese remainder theorem is proposed. The scheme can verify the remote password without verification tables. In the initial phase, the password generation centre generates and assigns a password corresponding to each user. The ideas of smart cards and the identity-based signature scheme introduced by Shamir are employed in this phase. Each user possesses a smart card for later login and authentication. In the login phase, the user submits the identity and password associated with the smart card. In the authentication phase, the system verifies the remotely submitted password to check if the login request is accepted or rejected. A signature scheme and communication timestamps are provided in the authentication phase against the potential attacks of replaying a previously intercepted login request.
RETRIEVING THE MOST SIMILAR SYMBOLIC PICTURES FROM PICTORIAL DATABASES
(1992-09-01)
CHANG, CC
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WU, TC
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
In this article, we suggest an iconic indexing mechanism for spatial similarity retrieval on iconic image databases based upon the spatial relationships among the objects in a picture. The iconic objects we deal with are some kinds of gross panorama of simple objects. We also assume that any one iconic object is not distinguished from any other object of the same kind. For our mechanism, we first transform each iconic picture into a set of ordered triples (O(i), O(j), R(ij)) where O(i) and O(j) are objects and R(ij) is the predefined spatial relationship codes between O(i) and O(j). Then we construct a set of hashing functions for all spatial relationship codes R(ij), separately, associated with all ordered pairs (O(i), O(j)) extracted from the ordered triples (O(i), O(j), R(ij)), Thereafter, an iconic index table can be established according to the constructed hashing functions for all predefined spatial relationship codes. By applying the constructed hashing functions, the most similar pictures in the database satisfying a specified query can be fast determined. We can easily extend our mechanism for handling the case when some new spatial relationship codes are defined later for the considerations of refined spatial similarity retrieval under the maximum-likelihood measure criterion.