Browsing by Author "Sun, HM"

Now showing 1 - 9 of 9

A note on breaking and repairing a secure broadcasting in large networks
(1999-01-25)
Sun, HM
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Shieh, SP
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Sun, HM
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資訊工程學系
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Department of Computer Science
In this note, we show that a proposed secure broadcasting scheme is insecure. We also present a modified scheme to overcome this weakness. The modified scheme has the extra advantage that each participant can derive his group keys from group identities without the need of knowing other information. (C) 1999 Elsevier Science BV. All rights reserved.
An efficient construction of perfect secret sharing schemes for graph-based structures
(1996-04-01)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
In this paper, we propose an efficient construction of perfect secret sharing schemes for graph-based access structures where a vertex denotes a participant and an edge does a qualified pair of participants. The secret sharing scheme is based on the assumptions that the pairs of participants corresponding to edges in the graph can compute the master key but the pairs of participants corresponding to nonedges in the graph cannot. The information rate of our scheme is 1/(n-1), where n is the number of participants. We also present an application of our scheme to the reduction of storage and computation loads on the communication granting server in a secure network.
Constructing perfect secret sharing schemes for general and uniform access structures
(1999-09-01)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
A perfect secret sharing scheme allows a secret K to be shared among a set of participants in such a way that only qualified subsets of participants can recover the secret, and unqualified subsets of participants obtain no information regarding the secret. In this paper, we propose a construction of perfect secret sharing schemes with uniform, generalized access structures of rank 3. Compared with other constructions, our construction has some improved lower bounds on the information rate. In addition, we also generalize the construction to perfect secret sharing schemes with uniform, generalized access structures of constant rank.
Digital multisignature schemes for authenticating delegates in mobile code systems
(2000-07-01)
Shieh, SP
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Lin, CT
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Yang, WB
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Sun, HM
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資訊工程學系
In this paper, we motivate the need for efficient multisignature schemes in delegated mobile services. With the schemes, delegates can be identified and delegated accesses can be controlled. First, we give a new digital signature scheme with message recovery. Based on the digital signature scheme, two digital multisignature schemes are proposed: the parallel multisignature scheme and the serial multisignature scheme. The parallel multisignature scheme allows each user to sign the same message separately and independently, and then combines all individual signatures into a multisignature, The serial multisignature scheme allows a group of users to sign the message serially, and does not need to predetermine the signing order. Both multisignature schemes tan withstand the attacks that aim to forge the signatures or to get the private kegs of the signers.
Optimal information-dispersal for increasing the reliability of a distributed service
(1997-12-01)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
This paper investigates the (m,n) information dispersal scheme (IDS) used to support fault-tolerant distributed servers in a distributed system. In an (m, n)-IDS, a file M is broken into n pieces such that any m pieces collected suffice for reconstructing M. The reliability of an (m, n)-IDS is primarily determined by 3 important factors: n = information dispersal degree (IDD), n/m = information expansion ratio (IER), P-a = success-probability of acquiring a correct piece. It is difficult to determine the optimal IDS with the highest reliability from very many choices. Our analysis shows: several novel features of (m, n)-IDS which can help reduce the complexity of finding the optimal IDS with the highest reliability; that an IDS with a higher IER might not have a higher reliability, even when P-s-->1. Based on the theorems given herein, we have developed a method that reduces the complexity for computing the highest reliability from, O(v) [v = number of servers] to O(1) when the 'upper bound of the IER' = 1, or O(v(2)) to O(1) when the 'upper bound of the IER' > 1.
Recursive constructions for perfect secret sharing schemes
(1999-02-01)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
A secret sharing scheme is a method which allows a secret to be shared among a set of participants in such a way that only qualified subsets of participants can recover the secret. A secret sharing scheme is called perfect if unqualified subsets of participants obtain no information regarding the secret. The information rate of a secret sharing scheme is defined to be the ratio between the size of secret and the maximum size of the shares. In this paper, we propose some recursive constructions for perfect secret sharing schemes with access structures of constant rank. Compared with the best previous constructions, our constructions have some improved lower bounds on the information rate. (C) 1999 Elsevier Science Ltd. All rights reserved.
Secret sharing schemes for graph-based prohibited structures
(1998-10-01)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
A secret sharing scheme for the prohibited structure is a method of sharing a master key among a finite set of participants in such a way that only certain prespecified subsets of participants cannot recover the master key. A secret sharing scheme is called perfect, if any subset of participants who cannot recover the master key obtains no information regarding the master key. In this paper, we propose an efficient construction of perfect secret sharing schemes for graph-based prohibited structures where a vertex denotes a participant and an edge does a pair of participants who cannot recover the master key. The information rate of our scheme is 2/n, where n is the number of participants. (C) 1998 Elsevier Science Ltd. All rights reserved.
Secret sharing schemes for graph-based prohibited structures
(1998-10-01)
Sun, HM
;
Shieh, SP
;
資訊工程學系
;
Department of Computer Science
A secret sharing scheme for the prohibited structure is a method of sharing a master key among a finite set of participants in such a way that only certain prespecified subsets of participants cannot recover the master key. A secret sharing scheme is called perfect, if any subset of participants who cannot recover the master key obtains no information regarding the master key. In this paper, we propose an efficient construction of perfect secret sharing schemes for graph-based prohibited structures where a vertex denotes a participant and an edge does a pair of participants who cannot recover the master key. The information rate of our scheme is 2/n, where n is the number of participants. (C) 1998 Elsevier Science Ltd. All rights reserved.
Secure broadcasting in large networks
(1998-03-25)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
It is common that users or hosts in a large network are partitioned and organized as a hierarchical tree where children of the same parent form a group. Secure broadcasting intends to provide a secure communication channel from a sending principal to a group of legal receiving principals. Only legal receiving principals can decrypt the message, and illegal receiving principals cannot acquire any information from the broadcasted message. In this paper, we propose a secure broadcasting protocol in which only one packet is transmitted for every broadcast, and the size of the broadcasted packet is small. (C) 1998 Elsevier Science B.V.