Browsing by Author "SUN, HM"

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CONSTRUCTION OF DYNAMIC THRESHOLD SCHEMES
(1994-11-24)
SUN, HM
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SHIEH, SP
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交大名義發表
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資訊工程學系
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National Chiao Tung University
An (m,n) threshold scheme is to decompose a shared secret into n shares in such a way that the shared secret cannot be reclaimed unless any m shares are collected. A new dynamic threshold scheme that allows the shared secret to be updated without changing the shares is proposed.
KEY GENERATION OF ALGEBRAIC-CODE CRYPTOSYSTEMS
(1994-01-01)
SUN, HM
;
HWANG, TN
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
The purpose of this paper is to efficiently generate large nonsingular matrix (S, S-1) pairs and permutation matrices over the binary field using short keys. The motivation of this work is to provide a solution to the long-key problem in algebraic-code cryptosystems. A special class of matrices which have exactly two 1's in each row and each column is defined, and their properties are investigated to facilitate the construction of these algorithms. The time complexities of these algorithms are studied and found to have O(n) n-bit word operations.
ON CONSTRUCTING SECRET SHARING SCHEMES
(1994)
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
ON DYNAMIC THRESHOLD SCHEMES
(1994-11-25)
SUN, HM
;
SHIEH, SP
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資訊工程學系
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Department of Computer Science
An (m, n) threshold scheme is to decompose the master key K into n secret shadows in such a way that the master key K cannot be reclaimed unless any m shadows are collected. However, any m-1 or fewer shadows provide absolutely no information about K. In 1989, Laih et al. proposed the concept of dynamic threshold schemes which allow the master key to be updated without changing the secret shadows. However, the perfect dynamic threshold scheme, which provides perfect secrecy though the master key is allowed to be changed, has not been proposed. Nor has any paper shown the existence of perfect dynamic threshold schemes. In this paper, we prove that perfect dynamic threshold schemes do not exist when their master keys need be updated [log(2)Llog(2)K] times or more without changing the secret shadows, where L is the secret shadow space and K is the master key space. Furthermore, we propose an perfect dynamic threshold scheme which allows its master key to be updated once without changing the secret shadows.