Certificate-based verifiably encrypted signatures from pairings

We propose a new verifiably encrypted signature scheme from pairings by choosing a certificate authority (CA) as an adjudicator. In this scheme, a certificate, or generally, a signature acts not only as the binding of the public key and its holder, but also as CA’s guarantee against partiality in adjudication. Under the CDH assumption and in the random oracle model, we show that the new scheme is EUF-CMA secure in a stronger security model. In this security model, there are three types of inside adversaries with more power than those in previous verifiably encrypted signature schemes. The proposed scheme can solve the authentication problem of public keys and relax excessive reliance on the trustworthiness of the adjudicator so that the adjudicator only needs to be trusted by the signer. Hence, the fair exchange protocols of signatures based on the new scheme is more trustworthy and practical than the previous ones.     

Efficient verifiably encrypted signatures from lattices

Verifiably encrypted signature schemes can convince a verifier that a given ciphertext is an encryption of an ordinary signature on a given message and the ordinary signature can be recovered by the third party, called adjudicator. In 2010, Rückert et al. proposed a general construction for the verifiably encrypted signatures, and then, they also showed that there exist the lattice-based verifiably encrypted signature schemes. Their constructions are very insightful, but their schemes need an extra adjudication setup phase and Merkle trees, so they have large parameters and keys, that is, they are inefficient. Also, their schemes provide only the limited signature capacity because the signing keys should be reissued after generating \(k\) th verifiably encrypted signatures. To overcome the weaknesses of Rückert et al.’s scheme, we construct a verifiably encrypted signature scheme based on the hard lattice problems. Our scheme provides the full functionality, i.e., the signatures can be generated without any limitations and does not need any extra adjudication setup phases. Moreover, the size of the secret keys in our scheme is constant. Our scheme provides unforgeability, opacity, extractability, and abuse-freeness in the random oracle model.     

Usable optimistic fair exchange

Fairly exchanging digital content is an everyday problem. It has been shown that fair exchange cannot be achieved without a trusted third party (called the Arbiter). Yet, even with a trusted party, it is still non-trivial to come up with an efficient solution, especially one that can be used in a p2p file sharing system with a high volume of data exchanged.We provide an efficient optimistic fair exchange mechanism for bartering digital files, where receiving a payment in return for a file (buying) is also considered fair. The exchange is optimistic, removing the need for the Arbiter’s involvement unless a dispute occurs. While the previous solutions employ costly cryptographic primitives for every file or block exchanged, our protocol employs them only once per peer, therefore achieving an O(n) efficiency improvement when n blocks are exchanged between two peers. Our protocol uses very efficient cryptography, making it perfectly suitable for a p-2-p file sharing system where tens of peers exchange thousands of blocks and they do not know beforehand which ones they will end up exchanging. Therefore, our system yields up to one-to-two orders of magnitude improvement in terms of both computation and communication (40 s vs. 42 min, 1.6 MB vs. 200 MB). Thus, for the first time, a provably secure (and privacy-respecting when payments are made using e-cash) fair exchange protocol can be used in real bartering applications (e.g., BitTorrent) [14] without sacrificing performance.     

一个高效的可验证加密签名方案

利用椭圆曲线上的双线性对,构造一个新的可验证加密签名方案,该方案在随机预言模型下具有不可伪造性和不透明性。由于该方案只有两次对运算,所以运算效率很高。可验证加密签名常用来构造优化公平交换协议,在电子商务领域里有着广泛应用。     

Group-oriented fair exchange of signatures

Optimistic Fair Exchange (OFE) of digital signatures allows two parties to exchange their signatures in a fair manner so that a third party, called the arbitrator, gets involved only when there is a dispute. Previous work on OFE considers the two parties as individuals and there is no formal study on the scenario where the two parties are two groups of users. In this paper, we formalize this new variant and call it a Group-oriented Optimistic Fair Exchange (GOFE). GOFE allows two users from two different groups to exchange signatures on behalf of their groups in a fair and anonymous manner. We formalize the notion by providing the first set of security models for GOFE, and show that it is closely related to Ambiguous OFE (AOFE) proposed by Huang et al. in Asiacrypt 2008. In particular, we propose a generic transformation which converts a GOFE to an AOFE. We also give an efficient and concrete GOFE construction and prove its security under the security models we defined. The security of the scheme relies on the decision linear assumption and strong Diffie-Hellman assumption in the random oracle model.     

Certificate-based fair exchange protocol of signatures from pairings

In 2003, Boneh et al. proposed the first non-interactive verifiably encrypted signature scheme that can be used to construct optimistic fair exchange protocols of signatures. However, their scheme depends on an entirely honest adjudicator, neither forging signatures nor colluding with one party. To eliminate this unrealistic premise, we propose a new paradigm for building fair exchange protocols of signatures from pairings by choosing a certificate authority CA as an adjudicator. In this paradigm, a certificate, or generally, a signature plays threefold role, firstly acts as the binding of the public key and its holder, secondly acts as a decryption key, and thirdly acts as CA’s guarantee against partiality in adjudication. The proposed protocol not only overcomes the classical authentication problem of public keys, but also relaxes excessive reliance on the trustworthiness of the adjudicator so that the adjudicator only needs to be trusted by the signer.     

An optimistic fair exchange protocol with active intermediaries

The study of business transactions is a topic of interest in the field of electronic commerce. Fair Exchange protocols deal with the problem of how the different parties involved in a transaction can exchange their parts securely, i.e., with assurance that the other parties will carry on with the transaction. Fair Exchange is a field of research that has been extensively studied, but we have found that previous proposals have failed to address one problem that concerns electronic commerce, i.e., transactions with active intermediaries. Previous Fair Exchange protocols deal with scenarios where only 2 parties are involved or scenarios where N known parties have to reach a common agreement, omitting scenarios where active intermediaries are involved. In this paper, we present an Optimistic Fair Exchange protocol for transactions with active intermediaries, which, to the best of our knowledge, is the first of its kind.     

高效的基于证书可验证加密签名方案

针对传统公钥密码体制中存在的公钥证书管理问题和基于身份密码体制中存在的密钥托管问题,以及互联网上交易过程中存在的不公平性,将基于证书签名体制(CBS)与可验证加密签名(VES)相结合,提出了一种基于证书可验证加密签名体制CBVES。首先,定义了基于证书可验证加密签名方案的安全模型;然后,基于k-CAA问题和Squ-CDH问题的困难性,构造一个新的基于证书的可验证加密签名方案,并在随机预言机模型下证明了其安全性。与已有的基于证书可验证加密签名方案相比,所提出的方案是高效的,所需的计算量小,且具有需要仲裁人和指定验证人合作才能从可验证加密签名提取普通签名的优点。     

对一个可验证加密签名方案的安全性分析

对Yang等最近提出的可验证加密签名方案进行了安全性分析,结论是虽然这个方案在标准模型下是可证明安全的,但是在多用户环境下容易遭受密钥替换攻击,即一个敌手能够生成一个新公钥满足合法签名者的可验证加密签名。给出了一个具体实例,说明容易遭受密钥替换攻击的可验证加密签名如果用于公平交换协议中,在多用户环境下会违背公平交换协议的公平性。     

安全有效的可验证加密签名方案

针对目前可验证加密签名方案的公平性完全依赖仲裁者中立问题,基于Shim的数字签名方案,提出一个安全有效的基于身份的可验证加密签名方案。方案中仲裁者对自己的保证书签名,有效地解决了仲裁者在解决冲突时拒绝恢复普通签名问题,从而加强了交换签名的公平性。与已有的方案相比,该方案不仅具有极少的对运算,而且具有更高的公平性。在CDH问题难解的假设下,该方案在随机预言模型中可证明是安全的。     

基于身份的签名和可验证加密签名方案*

基于双线性对,提出了一个基于身份的签名方案,在计算性D iffie-Hellman问题困难的假设下,证明了该方案在随机预言机模型下抗适应性选择消息和身份攻击。基于提出的方案,构造了一个可证安全的可验证加密签名方案,其不可伪造性依赖于提出的基于身份的签名方案,不透明性依赖于基于身份的签名方案和BLS短签名。与已有方案相比,该方案的优势是基于身份,不需要证书,从而简化了密钥管理。     

A new efficient optimistic fair exchange protocol without random oracles

Optimistic fair exchange (OFE) is a kind of protocols to solve the problem of fair exchange between two parties. Most of the previous work on this topic are provably secure in the random oracle model. In this work, we propose a new construction of OFE from another cryptographic primitive, called time capsule signature. The construction is efficient and brings almost no overhead other than the primitive itself. The security of our new construction is based on that of the underlying primitive without relying on the random oracle heuristic. Applying our generic construction to the time capsule signature scheme recently proposed by Libert and Quisquater, we obtain a new concrete and efficient OFE construction secure based on Computational Diffie–Hellman assumption in the standard model.     

一种基于BLS签名的优化公平交换协议

公平交换协议是构造电子商务系统的最基本工具。BLS短签名是双线性密码学中应用最为广泛的密码元件之一。基于BLS短签名,提出了一种优化公平交换协议,并分析了其安全性与运行效率。     

盲化的基于无证书的可验证加密签名方案

可验证加密签名方案的公平性完全由仲裁者中立问题决定,这样就降低了交换签名的安全性。为了应对这种情况,利用双线性对的性质,结合无证书公钥密码体制与可验证加密数字签名,设计了一种盲化的基于无证书的可验证加密签名方案,方案中的仲裁者不能直接恢复原始签名,从而加强了交换签名的安全性。在假设离散对数问题(DLP)和计算Diffie-Hellman问题(CDHP)难解的前提下,该方案在随机预言模型中是可证安全的。     

新的公平数字签名交换方案

基于Gorantla等最近提出的标准模型下可证安全的可验证加密签名,提出了一个优化的公平数字签名交换方案。签名交换双方首先交换他们的可验证加密签名,验证通过以后再交换他们的真实签名,如果其中一方不能诚实地执行协议,则另一方可求助可信任第三方以达到公平交换的目的。提出的方案具有签名长度短、计算量小等优点,可以公平且有效地实现数字签名的交换。     

安全有效的代理可验证加密签名方案

结合可验证加密签名方案和代理数字签名方案,提出了一个基于证书的代理可验证加密签名方案,并对该方案的正确性进行了分析,证明了该方案的安全性。     

An efficient secure proxy verifiably encrypted signature scheme

Verifiably encrypted signature is an important cryptographic primitive, it can convince a verifier that a given ciphertext is an encryption of signature on a given message. It is often used as a building block to construct an optimistic fair exchange. In this paper, we propose a new concept: a proxy verifiably encrypted signature scheme, by combining proxy signature with a verifiably encrypted signature. And we formalize security model of proxy verifiably encrypted signature. After a detail construction is given, we show that the proposed scheme is provably secure in the random oracle model. The security of the scheme is related to the computational Diffie–Hellman problem.     

Fast homomorphic SVM inference on encrypted data

Neural Computing and Applications - Kernel methods are popular machine learning methods that provide automated pattern analysis of raw datasets. Of particular interest is Support Vector Machines...     

Separable reversible data hiding in homomorphic encrypted domain using POB number system

Multimedia Tools and Applications - In this paper, a novel separable reversible data hiding in homomorphic encrypted images (RDHEI) using POB number system is proposed. The frame of the proposed...     

A homomorphic encrypted reversible information hiding scheme for integrity authentication and piracy tracing

Reversible information hiding plays an important roles in the field of privacy protection. In this paper, a new reversible information hiding scheme is proposed which supports the direct operation in homomorphic encrypted domain. The proposed “Joint Hiding and Tracing, JHT” tactics and the “3 Level Integrity Authentication Scheme” devote to piracy tracing and integrity authentication. To enhance security, the Paillier homomorphic encryption and Arnold technology are employed. Furthermore, we present the dual region division tactics including Data/Signature region division and Texture/Smooth region division. Data/Signature region division is to circumvent conflicts, and Texture/Smooth region division is fit well with the human visual characteristics. Besides, neighboring quadratic optimization approach is presented to eliminate the smooth/texture isolated islands in the texture/smooth regions. In addition, Extended Integer Transform and position image are developed to achieve reversibility and circumvent overflow/underflow problems. Experimental results confirm the efficient of the proposed scheme, and demonstrate it not only realizes privacy protection, integrity authentication and piracy tracing, but also holds the characteristics of higher security, larger capacity and better restoration quality.