An efficient threshold key-insulated signature scheme

To tackle the key-exposure problem in signature settings, this paper introduces a new cryptographic primitive named threshold key-insulated signature (TKIS) and proposes a concrete TKIS scheme. For a TKIS system, at least k out of n helpers are needed to update a user’s temporary private key. On the one hand, even if up to k−1 helpers are compromised in addition to the exposure of any of temporary private keys, security of the non-exposed periods is still assured. On the other hand, even if all the n helpers are compromised, we can still ensure the security of all periods as long as none of temporary private keys is exposed. Compared with traditional key-insulated signature (KIS) schemes, the proposed TKIS scheme not only greatly enhances the security of the system, but also provides flexibility and efficiency.     

Identity-based key-insulated proxy signature without random oracles

In an identity based proxy signature (IBPS) scheme, a designated proxy signer can generate the signature on behalf of an original signer. Traditional IBPS schemes normally rely on the assumption that private keys are kept perfectly secure. However, due to viruses, worms or other break-ins allowed by operating-system holes, key exposure seems inevitable. To minimize the damage caused by key exposure in IBPS, we propose an identity-based key-insulated proxy signature (IBKIPS) scheme in the standard model, i.e. without random oracles.     

Universally composable proactive threshold RSA signature

Recently some efforts were made towards capturing the security requirements within the composable security framework.This modeling has some significant advantages in designing and analyzing complex systems.The threshold signature was discussed and a definition was given based on the universal composability framework, which is proved to be equivalent to the standard security definition.Furthermore, a simple, effcient and proactive threshold RSA signature protocol was presented.It is proved to be correct, consistent and unforgeable relative to the environment that at most t-1 parties are corrupted in each proactive stage.It is also secure under the universal composability framework.It is a UC based security and is proved to be equivalent to the standard security.     

Distributed certificateless key encapsulation mechanism secure against the adaptive adversary

This paper proposes an adaptively secure solution to certificateless distributed key encapsulation mechanism from pairings by using Canetti's adaptive secure key generation scheme based on discrete logarithm. The proposed scheme can withstand adaptive attackers that can choose players for corruption at any time during the run of the protocol, and this kind of attack is powerful and realistic. In contrast, all previously presented threshold certificateless public key cryptosystems are proven secure against the more idealized static adversaries only. They choose and fix the subset of target players before running the protocol. We also prove security of this scheme in the random oracle model.     

ID-Based Threshold Decryption Secure Against Chosen Plaintext Attack

Introduction Inthresholddecryptioncryptosystems,the powertodecryptissharedamongasetofdecryp-tionservers.In2001,D.BonehandM.Franklin proposedapracticalidentity-basedencryption(IBE)schemefromtheweilpairing.Combining thetwoconceptstogether,some“ID-basedthresh-olddecryption”schemeshavebeenconstructed.In suchschemes,anentity'spublickeyisderiveddi-rectlyfromitsidentity.Atrustedthirdparty calledtheprivatekeygenerator(PKG)usesthe masterkeytogenerateprivatekeysforallentities.Eachdecryptionserve…     

Strong key-insulated signature in the standard model

The only known construction of key-insulated signature (KIS) that can be proven secure in the standard model is based on the approach of using double signing. That is, the scheme requires two signatures: a signature with a master key and a signature with the signer’s secret key. This folklore construction method leads to an inefficient scheme. Therefore it is desirable to devise an efficient KIS scheme. We present the first scheme with such a construction. Our construction derives from some variations of the Waters’ signature scheme. It is computationally efficient and the signatures are short. The scheme is provably secure based on the difficulty of computational Diffie-Hellman (CDH) problem in the standard model.     

“两会”盛大开幕 国车精品保驾护航

龙威客车“两会”再展金龙风采 近年来．几乎国内所有重大活动．我们都能见到“金龙”车队闪亮、浩荡的英姿．这不仅彰显了金龙客车卓越的技术及安全性能和高品质的品牌优势．更为大金龙身为行业龙头企业的雄厚实力做出了最佳注脚。自3月3日以来．14辆来自北汽旅游汽车公司的金龙”龙威“XMQ6129Y客车．为参加两会的福建、山东、江西等多个代表团提供全程交通运输服务．这款寄托着大金龙人汗水与创造力的新型客车．不仅接受着代表们的检验．同时也在接受着同行竞争者的检验。     

On constructing certificateless proxy signature from certificateless signature

In proxy signature schemes, an original signer A delegates its signing capability to a proxy signer B, in such a way that B can sign message on behalf of A.The recipient of the final message verifies at the same time that B computes the signature and that A has delegated its signing capability to B.Recently many identity-based(ID-based) proxy signature schemes have been proposed, however, the problem of key escrow is inherent in this setting.Certificateless cryptography can overcome the key escrow problem.In this paper, we present a general security model for certificateless proxy signature scheme.Then, we give a method to construct a secure certificateless proxy scheme from a secure certificateless signature scheme, and prove that the security of the construction can be reduced to the security of the original certificateless signature scheme.     

New constructions of dynamic threshold cryptosystem

This study deals with the dynamic property of threshold cryptosystem. A dynamic threshold cryptosystem allows the sender to choose the authorized decryption group and the threshold value for each message dynamically. We first introduce an identity based dynamic threshold cryptosystem, and then use the Canetti- Halevi-Katz （CHK） transformation to transform it into a fully secure system in the traditional public key setting. Finally, the elegant dual system encryption technique is applied to constructing a fully secure dynamic threshold cryptosystem with adaptive security.     

Attribute-based signature on lattices

Attribute-based signature is a versatile class of digital signatures. In attribute-based signature, a signer obtains his private key corresponding to the set of his attributes from a trusted authority, and then he can sign a message with any predicate that is satisfied by his attributes set. Unfortunately, there does not exist an attribute- based signature which is resistance to the quantum attacks. This means we do not have secure attribute-based signature schemes in a post-quantum world. Based on this consideration, an attribute-based signature on lattices, which could resist quantum attacks, is proposed. This scheme employs ＂bonsai tree＂ techniques, and could be proved secure under the hardness assumption of small integer solution problem.