Browsing by Author "Hwang, MS"

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A new key authentication scheme based on discrete logarithms
(2003-07-15)
Lee, CC
;
Hwang, MS
;
Li, LH
;
資訊工程學系
;
Department of Computer Science
In this article, we propose a new public key authentication scheme for cryptosystems with a trusty server. The scheme is based on discrete logarithms. In the scheme, the certificate of the public key is a combination of user's password and private key. The scheme not only resolve the problems appeared but also is secure for the others public-key authentication. (C) 2002 Elsevier Science Inc. All rights reserved.
A new privacy and authentication protocol for end-to-end mobile users
(2003-11-01)
Lee, CC
;
Yang, CC
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
In this papecr. we propose a new privacy and authentication scheme for end-to-end mobile users. There are three goals in our scheme. The first allows two end-to-end mobile users to communicate privately each other. The second allows two end-to-end mobile users to distribute a session key simply. The third allows two end-to-end mobile users to mutually authenticate. Copyright (C) 2003 John Wiley Sons, Ltd.
A novel application of the phone card and its authentication in mobile communications
(1999-07-01)
Lee, CH
;
Hwang, MS
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
The Subscriber Identity Module (SIM) is conventionally used in wireless communication systems. However, several limitations involving SIM significantly reduce public access in wireless communications. This study examined the feasibility of using public telephone cards in wireless communications. This novel application retains the merits of SIM. Among the relevent issues addressed are location tracking of the user, authentication of the phone card, and the billing scheme. Moreover, two implementations of phone card authentication are presented.
A simple remote user authentication scheme
(2002-07-01)
Hwang, MS
;
Lee, CC
;
Tang, YL
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資訊工程學系
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Department of Computer Science
In this article, we propose a simple remote user authentication scheme using smart cards. This scheme has the following features. First, it does not require any password or verification tables. Second, it can withstand the message replay attack. Third, any legal users can arbitrarily choose and change their own passwords at will. And finally, the password of a user is not revealed to the server. In addition, the computational costs of this scheme are less than those of any previously proposed schemes. (C) 2002 Elsevier Science Ltd. All rights reserved.
A threshold signature scheme for group communications without a shared distribution center
(2004-08-01)
Chang, TY
;
Yang, CC
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
In this paper, we shall propose a (t, n) threshold signature with (k, l) threshold-shared verification to be used in a group-oriented cryptosystem without a shared distribution center (SDC). In this scheme, any t participants can represent a group (signing group) to sign a message, and any k participants can represent another group (verifying group) to verify the signature. We need no SDC to distribute the public and private keys to all the participants in the two groups. Hence, our scheme is more practical in real-world applications and more efficient than its predecessors in terms of communication and computational complexity as well as storage. (C) 2003 Elsevier B.V. All rights reserved.
An access control scheme based on Chinese remainder theorem and time stamp concept
(1996)
Hwang, MS
;
Tzeng, WG
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
In this paper we propose a new dynamic access control method for the computer system with frequently inserted, deleted and updated users/files. Our method, based on the concepts of the access control matrix, key-lock-pair, time stamp and Chinese remainder theorem, associates each user with a user key and a user lock and each tile with a file key and a file lock Our method can achieve the following four goals. (1) By a simple module operation on the keys and locks of the user and the file, we can reveal the access right of a user to a file. (2) When a user/file is added to the computer system, we only assign a key and a lock to the user/file without affecting the keys and locks of the other users/files in the system. (3) When a user/file is deleted from the computer system, we simply erase the entry of the user/file in the computer system. (4) When the access right of a user to a file is updated, we merely modify the key and lock of the user or the file without affecting the keys and locks of the other users/files in the system. The main contribution of our method is that the action of inserting, deleting a user/file, or updating the access right of a user to a file can be done by modifying only one key and one lock, which could not be achieved simultaneously before.
An improvement of mobile users authentication in the integration enviromnents
(2002)
Hwang, MS
;
Lee, CC
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
This paper shows that Tzeng and Tzeng's protocol has a drawback that the protocol can be easily crashed by an evil VLR attack. Therefore, we propose a slight modification to their protocol to improve their shortcoming. As a result, our protocol does not only enhance the security of Tzeng and Tzeng's protocol but also improves the efficiency.
An improvement on the Lin-Wu (t, n) threshold verifiable multi-secret sharing scheme
(2005-04-05)
Chang, TY
;
Hwang, MS
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
Lin and Wu [IEE Proc. Comput. Digit. Tech. 146 (1999) 264] have proposed an efficient (t, n) threshold verifiable multi-secret sharing (VMSS) scheme based on the factorization problem and the discrete logarithm modulo a large composite problem. In their scheme, the dealer can arbitrarily give any set Of multiple secrets to be shared, and only one reusable secret shadow is to be kept by every participant. On the other hand, they have claimed that their scheme can provide an efficient solution to the cheating problems between the dealer and any participant. However, He and Wu [IEE Proc. Comput. Digit. Tech. 148 (2001) 139] have shown that Lin and Wu's scheme is in fact insecure against a cheating participant. In this paper, we shall try to improve the security of Lin and Wu's scheme while providing more efficient performance than other VMSS schemes in terms Of computational complexity. (C) 2004 Elsevier Inc. All rights reserved.
An untraceable blind signature scheme
(2003-07-01)
Hwang, MS
;
Lee, CC
;
Lai, YC
;
資訊工程學系
;
Department of Computer Science
In this paper, the authors intend to propose a new untraceable blind signature scheme based on the RSA cryptosystem. This paper applies the Extended Euclidean algorithm to our blind signature scheme. Compared with other blind signature schemes, our proposed scheme can meet the all requirements of a blind signature scheme. The security of the proposed scheme, as did that of the RSA cryptosystem, depends on the difficulty of solving the factoring problem.
Broadcasting cryptosystem in computer networks using geometric properties of lines
(2002-05-01)
Hwang, MS
;
Lee, CC
;
Chang, TY
;
資訊工程學系
;
Department of Computer Science
In 1997, Wu and Wu proposed an improvement of the Chang-Wu broadcasting cryptosystem using geometric properties of lines. The Wu-Wu scheme gave a better performance and required fewer public parameters than the Chang-Wu scheme. In this paper the authors propose an improvement to the Wu-Wu scheme using geometric properties of line. This improvement reduces the computation and significantly decreases the parameters required as compared to the Wu-Wu scheme.
Controlling access in large partially ordered hierarchies using cryptographic keys
(2003-08-15)
Hwang, MS
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
The problem of access control in a hierarchy is present in many application areas. Since computing resources have grown tremendously, access control is more frequently required in areas such as computer networks, database management systems, and operating systems. Many schemes based on cryptography have been proposed to solve this problem. However, previous schemes need large values associated with each security class. In this paper, we propose a new scheme to solve this problem achieving the following two goals. One is that the number of keys is reduced without affecting the security of the system. The other goal is that when a security class is added to the system, we need only update a few keys of the related security classes with simple operations. (C) 2002 Elsevier Inc. All rights reserved.
Cryptanalysis of publicly verifiable authenticated encryption
(2004-06-01)
Chang, TY
;
Yang, CC
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
Recently, Ma and Chen proposed a new authenticated encryption scheme with public verifiability. The signer can generate a signature with message recovery for a specified recipient. With a dispute, the recipient has ability to convert the signature into an ordinary one that can be verified by anyone without divulging her/his private key and the message. However, we point out that any adversary can forge a converted signature in this article.
Cryptanalysis of simple authenticated key agreement protocols
(2004-08-01)
Yang, CC
;
Chang, TY
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Hwang, MS
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資訊工程學系
;
Department of Computer Science
In this article, we will present a modification attack and a dictionary attack to subvert the security of the Tseng scheme and the Ku-Wang scheme. As we know, no existing schemes of simple authenticated key agreement protocols can successfully withstand our modification attack.
Cryptanalysis of the Hwang-Shi proxy signature scheme
(2002-11-01)
Hwang, MS
;
Lee, CC
;
Hwang, SJ
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資訊工程學系
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Department of Computer Science
Recently, Hwang and Shi proposed an efficient proxy signature scheme without using one-way hash functions. In their scheme, an original signer needn't send a proxy certificate to a proxy signer through secure channels. However, there are two public key substitution methods that can be used to attack their scheme. In this article, we show that their scheme is vulnerable to the public key substitution attacks.
Enhanced privacy and authentication for the global system for mobile communications
(1999)
Lee, CH
;
Hwang, MS
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
The Global System for Mobile Communications (GSM) is widely recognized as the modern digital mobile network architecture. Increasing market demands point toward the relevancy of security-related issues in communications. The security requirements of mobile communications for the mobile users include: (1) the authentication of the mobile user and Visitor Location Register/Home Location Register; (2) the data confidentiality between mobile station and Visitor Location Register, and the data confidentiality between Visitor Location Register and Visitor Location Register/Home Location Register (VLR/HLR); (3) the location privacy of mobile user. However, GSM does not provide enough security functions to meet these requirements. We propose three improved methods to enhance the security, to reduce the storage space, to eliminate the sensitive information stored in VLR, and consequently to improve the performance of the system. Proposed methods include an improved authentication protocol for the mobile station, a data confidentiality protocol, and a location privacy protocol. The merit of the proposed methods is to improve but not to alter the existing architecture of the system. Furthermore, this study also performs computational and capacity analyses to evaluate the original GSM system and proposed approaches on a comparative basis.
Improved Yen-Joye's authenticated multiple-key agreement protocol
(2002-11-07)
Hwang, MS
;
Lin, CW
;
Lee, CC
;
資訊工程學系
;
Department of Computer Science
An authenticated multiple-key agreement protocol is proposed. The protocol is not only secure against the unknown-key attack but also more efficient than other protocols.
Multilevel secure database encryption with subkeys
(1997-04-01)
Hwang, MS
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a multilevel database encryption system with subkeys. This new system is called the record-oriented cryptosystem which encrypts each record with different field-subkeys according to a security class of the data element. Each field is decrypted individually by the field-subkeys of which security class is higher than or equal to that of the encrypted field-subkeys. This system is based on the Chinese Remainder Theorem. Our scheme can protect the finest level of granularity such as relation level, attribute level, tuple level, or data element level in the relational database model.
Multilevel secure database encryption with subkeys
(1997-04-01)
Hwang, MS
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a multilevel database encryption system with subkeys. This new system is called the record-oriented cryptosystem which encrypts each record with different field-subkeys according to a security class of the data element. Each field is decrypted individually by the field-subkeys of which security class is higher than or equal to that of the encrypted field-subkeys. This system is based on the Chinese Remainder Theorem. Our scheme can protect the finest level of granularity such as relation level, attribute level, tuple level, or data element level in the relational database model.
New anonymous channel protocol in wireless communications
(2004)
Hwang, MS
;
Lee, CC
;
Lee, JZ
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資訊工程學系
;
Department of Computer Science
In this paper, the authors shall propose a new anonymous channel protocol for wireless communications. Compared with Juang et al.'s protocol and Jan et al.'s protocol, our protocot is more efficient. In addition, our protocol saves the trouble of employing public key cryptography in the anonymous channel ticket authentication phase just as Jan et al.'s protocol.
Security of improvement on methods for protecting password transmission
(2003)
Yang, CC
;
Chang, TY
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
Recently, Tseng et al. proposed an improvement on Peyravian and Zunic's protected password transmission scheme and protected changing scheme to remove some security flaws. However, as we will point out in this paper, any adversary can intercept the request for changing the password sent by a legal user and modify it with a wrong password. Furthermore, we shall also propose an improved version of their protected password changing scheme to help it out of the trouble.