Verifiably Encrypted Signatures Without Random Oracles

Introduction SincethepioneeringworkduetoBonehand Franklin[1],bilinearmapshavebecomeaveryfash-ionablebuildingblockandallowedtheopeningup ofcompletelynewterritoryincryptography,mak-ingitpossibletodesigncryptographicprimitives thatwerepreviouslyunknownorimpractical,for instance,identity-basedcryptosystem,ringsigna-tures,andshortsignatures,etc[2-6].Therearemanyapplicationsfordigitalsigna-tureswithsmallsize,suchaslow-bandwidthcom-municationenvironments.Thefirstpairing-based shortsignatureschemepro…     

Democratic group signatures with linkability from gap Diffie-Hellman group

Democratic group signatures(DGSs) attract many researchers due to their appealing properties, i.e., anonymity, traceability and no group manager.Security results of existing work are based on decisional Diffie-Hellman(DDH) assumption.In this paper, we present a democratic group signature scheme based on any gap Diffie-Hellman(GDH) group where DDH problem is easily but computational Diffie-Hellman(CDH) problem is hard to be solved.Besides the properties of ordinary DGSs, our scheme also provides the property of linkability, i.e., any public verifier can tell whether two group signatures are generated using the same private key.Security properties of our scheme employ a new and independently interesting decisional product Diffie-Hellman(DPDH) assumption which is weaker than DDH one.     

Provably Secure Short Proxy Signature Scheme from Bilinear Maps

An enhanced formal model of security for proxy signature schemes is presented and a provably secure short proxy signature scheme is proposed from bilinear maps. The proposed proxy signature scheme is based on two short secure signature schemes. One is used for delegating the signing rights and computing the standard signature; the other is used for computing proxy signature. Finally, a security proof of the proposed proxy signature scheme is showed by reducing tightly the security of the proposed proxy signature scheme to the security of the two basic signature schemes. The proposed proxy signature scheme has the shortest ordinary signatures and proxy signatures. Moreover, the proxy signature generation needs no pairing operation and verification needs just two pairing operation.     

Identity-based verifiably committed signature scheme without random oracles

An identity-based verifiably committed signature scheme （IB-VCS） was proposed, which is proved secure in the standard model （i.e., without random oracles）. It enjoys the setup-free property and stand-alone property, both of which make an exchange protocol more practical. The scheme is unconditionally secure against the cheating signer, its security against the cheating verifier is reduced to the computational Diffie-Hellman （CDH） problem in the underlying group, it is secure against the cheating trusted third party if the underlying Paterson Schuldt＇s identity based signature （IBS） scheme is secure, which is proven true based on the CDH assumption in the standard model.     

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.     

Provably secure and efficient proxy signature with untrustworthy proxy signer

Proxy signature has drawn great concerns.However, there still remains a challenge to construct a provably secure and effcient proxy signature scheme.In this paper, we propose an effcient proxy signature scheme based on factoring, and prove that it is secure in the random oracle.Furthermore, we present a new type of proxy signature, called Proxy Signature with Untrustworthy Proxy Signer, and construct a concrete scheme.     

An Efficient Provable Secure ID-Based Proxy Signature Scheme Based on CDH Assumption

IntroductionMambo, et al.[1]first introduced the conceptof proxy signature. In their scheme, an originalsigner delegates his signing right to a proxy signerin such a way that the proxy signer can sign anymessage on behalf of the original signer and theverifier can verify and distinguish proxy signaturefrom original signature. Proxy signature is of greatuse in such a case that a manager needs to autho-rize his secretary to sign documents on behalf ofhimself before his leaving for a vacation. Du…     

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.     

Certificateless message recovery signatures providing girault’s level-3 security

A digital signature with message recovery is a signature that the message itself (or partial of the message) is not required to be transmitted together with the signature. It has the advantage of small data size of communication comparing with the traditional digital signatures. In this paper, combining both advantages of the message recovery signatures and the certificateless cryptography, we propose the first certificatelss signature scheme with message recovery. The remarkable feature of our scheme is that it can achieve Girault’s Level-3 security while the conventional certificateless signature scheme only achieves Level-2 security. The security of the scheme is rigorously proved in the random oracle model based on the hardness of the k bilinear Diffie-Hellman inverse (k-BDHI) problem.     

基于可控量子隐形传态的代理签名方案

提出了一种量子代理签名方案．基于可控量子隐形传态，采用3粒子纠缠态作为量子信道，不同于经典的基于计算复杂性的代理签名方案，本方案利用量子隐形传态的物理特性来实现签名及验证，具有无条件安全性．     

Cryptanalysis of One Fair E-cash System

Introduction The concept of group signature was intro-duced by Chaum and Heyst[1], which allows indi-vidual members to make signatures on behalf of thegroup. More formally, a secure group signaturescheme must satisfy such properties as unforgeabil-ity, anonymity, traceability, coalition-resistance,unlinkability, exculpability[2,3]. An important application of group signature isto construct fair e-cash systems. A fair electroniccash system is a system that allows customers tomake payments anon…     

Improved ID-Based Signature Scheme Solving Key Escrow

Introduction Inatraditionalpublickeycryptosystem(PKC),theassociationbetweenauser'sidentity andhispublickeyisobtainedthroughadigitalcer-tificateissuedbyacertificationauthority(CA).TheCAchecksthecredentialsofauserbeforeis-suingacertificatetohim.Tosimplifythecertifi-catemanagementprocess,Shamir[1]introducedthe conceptofID-basedcryptosystemin1984,which allowedforauser'sidentityinformationsuchas hisname,IPaddress,telephonenumber,email address,etc.toserveashispublickey.Sucha publickeyisclearlyb…     

一种基于离散对数问题的存根代理盲签名方案

数字签名用来保证原始数据完整性和有效性,一个数字签名方案包括数字签名生成算法和数字签名验证算法.简短地介绍了盲签名、代理签名的基本思想和基本性质,并给出如何通过非对称密码算法的思想来实现这些签名方案,提出并详细介绍了一种基于离散对数问题的有存根的(免责声明)代理盲签名方案,讨论了基于离散对数问题的密码学算法的可能攻击方法,在此基础上给出了协议实现时的一些有益的建议.     

对两种代理盲签名体制的密码学分析

代理盲签名结合了代理签名与盲签名的优点，而多级代理签名实现了签名权利在许可范围内逐级向下代理的要求。利用椭圆曲线上的双线性对，陈玲玲等人提出了一种基于身份的代理盲签名方案，胡江红等人提出了一种基于身份的多级强代理盲签名方案。给出了这两个方案的密码学分析，指出在陈玲玲等人的方案中，代理签名人可以利用授权证书计算得到原始签名人的私钥，从而可直接伪造原始签名人的签名或授权，同时指出所提的两个方案也无法满足不可追踪性．代理签名人可以将自己在签名协议中的签名和签名的消息联系起来从而跟踪消息的拥有者，从而证明了这两个方案是不安全的。     

Certificateless strong key-insulated signature without random oracles

It is important to ensure the private key secure in cryptosystem. To reduce the underlying danger caused by the private key leakage, Dodis et al. (2003) introduced the notion of key-insulated security. To handle the private key leakage problems in certificateless signature schemes, we propose a new certificateless strong key-insulated signature scheme. Our scheme has two desirable properties. First, its security can be proved without utilizing the random oracle model. Second, it solves the key escrow problems in identity-based key-insulated signatures (IBKISs).     

Efficient and provably-secure certificateless proxy re-encryption scheme for secure cloud data sharing

In current cloud computing system, large amounts of sensitive data are shared to other cloud users. To keep these data confidentiality, data owners should encrypt their data before outsourcing. We choose proxy reencryption （PRE） as the cloud data encryption technique. In a PRE system, a semi-trusted proxy can transform a ciphertext under one public key into a ciphertext of the same message under another public key, but the proxy cannot gain any information about the message. In this paper, we propose a certificateless PRE （CL-PRE） scheme without pairings. The security of the proposed scheme can be proved to be equivalent to the computational Dire- Hellman （CDH） problem in the random oracle model. Compared with other existing CL-PRE schemes, our scheme requires less computation cost and is significantly more efficient. The new scheme does not need the public key certificates to guarantee validity of public keys and solves the key escrow problem in identity-based public key cryptography.     

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.     

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.     

一种高效的基于身份的代理盲签名方案

在代理签名中,原始签名人能将数字签名的权力委托给代理签名人;而在盲签名方案中,签名者不能看到被签消息的内容。签名被接受者得到后,签名者不能追踪签名,结合代理签名与盲签名的优点,利用基于椭圆曲线上的Weil配对（WeilPair—ing）的双线性映射,构造了一个高效的基于身份的代理盲签名方案．分析表明,该方案不仅满足代理盲签名所要求的所有性质,而且其效率也优于已有同类方案．     

A universal composability framework for analysis of proxy threshold signature

The universal composability framework is a new approach for designing and analyzing the security of cryptographic protocols. In this framework, the security of protocols is maintained under a general protocol composition operation. In the paper, we propose the universal composability framework for the analysis of proxy threshold signature and present a universally composable secure proxy threshold signature scheme which is the first one in this area. The proposed scheme is suitable for the mobile agents, which should migrate across different environment through network. Furthermore, we give the concrete analysis of the reduction to prove the security of the proposed scheme.