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Research On Security And Applications Of Threshold Cryptosystem

Posted on:2008-02-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z C ChaiFull Text:PDF
GTID:1118360215476822Subject:Computer software and theory
Abstract/Summary:PDF Full Text Request
Based on the secret sharing scheme proposed by Shamir in 1979, Desmedt et al presented the idea of threshold cryptography. In a threshold cryptosystem, a secret key associated with a single public key is distributed among a group of users. Only if a predetermined number of users cooperate, can they perform some crypto-operations, such as decrypting or signing. Due to its special structure, threshold cryptography has drawn great attentions since it was proposed. Currently, threshold cryptography has been used in key escrow, key recovery, distribution of power, and etc. A lot of new features have been added to threshold schemes, such as dynamic threshold and public verifiable shares. However, with the advance of ID-based cryptography and the maturity of proven security, it is desirable to design threshold scheme in ID-based setting that is preferably proven secure without random oracle model. Meanwhile, the fixed single public key are not suitable for applications in dynamic groups, so it needs to extend the threshold system to multi-users settings. Also, threshold cryptography can be considered as solutions for security issues of emerging technology. This work is carried out to deal with issues mentioned above.The contributions are summarized as follows:1. Analyze the security model of ID-based threshold decryption scheme, and propose a scheme that is proven secure without random oracle model. The scheme obtains a special security feature that a single private key can not be derived even all the private key shares are gathered. The scheme is also proposed to be used in key escrow.2.Aim to solve the security issue in dynamic groups, the traditional threshold encryption has been extend to multi-receiver settings. In a ID-based multi-receiver threshold encryption scheme, a send will first collect a list of receivers' identities(the public keys), then use these identities to encrypt the message. Only when a number of users listed in these identities cooperate, can they read message. The security model and an efficient scheme with only one pairing computation are proposed. 3. Propose a forward secure proxy signature scheme based on factoring problem, and then extend the scheme to threshold forward secure proxy signature scheme.4.To meet the requirements of both security and availability in some special environment, such as Ad hoc networks, two password based threshold authentication schemes were proposed. The securities of these two schemes are based on factoring and logarithm problem respectively. The detailed security and efficiency analysis are also presented.
Keywords/Search Tags:public-key cryptography, threshold cryptography, ID based cryptography, password based authentication, provable security
PDF Full Text Request
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