908 research outputs found

    Aggregatable Certificateless Designated Verifier Signature

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    In recent years, the Internet of Things (IoT) devices have become increasingly deployed in many industries and generated a large amount of data that needs to be processed in a timely and efficient manner. Using aggregate signatures, it provides a secure and efficient way to handle large numbers of digital signatures with the same message. Recently, the privacy issue has been concerned about the topic of data sharing on the cloud. To provide the integrity, authenticity, authority, and privacy on the data sharing in the cloud storage, the notion of an aggregatable certificateless designated verifier signature scheme (ACLDVS) was proposed. ACLDVS also is a perfect tool to enable efficient privacy-preserving authentication systems for IoT and or the vehicular ad hoc networks (VANET). Our concrete scheme was proved to be secured underling of the Computational Diffie-Hellman assumption. Compared to other related schemes, our scheme is efficient, and the signature size is considerably short

    Searchable atribute-based mechanism with efficiient data sharing for secure cloud storage

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    To date, the growth of electronic personal data leads to a trend that data owners prefer to remotely outsource their data to clouds for the enjoyment of the high-quality retrieval and storage service without worrying the burden of local data management and maintenance. However, secure share and search for the outsourced data is a formidable task, which may easily incur the leakage of sensitive personal information. Efficient data sharing and searching with security is of critical importance. This paper, for the first time, proposes a searchable attribute-based proxy re-encryption system. When compared to existing systems only supporting either searchable attribute-based functionality or attribute-based proxy re-encryption, our new primitive supports both abilities and provides flexible keyword update service. Specifically, the system enables a data owner to efficiently share his data to a specified group of users matching a sharing policy and meanwhile, the data will maintain its searchable property but also the corresponding search keyword(s) can be updated after the data sharing. The new mechanism is applicable to many real-world applications, such as electronic health record systems. It is also proved chosen ciphertext secure in the random oracle model

    Identity-based data storage in cloud computing

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    Identity-based proxy re-encryption schemes have been proposed to shift the burden of managing numerous files from the owner to a proxy server. Nevertheless, the existing solutions suffer from several drawbacks. First, the access permission is determined by the central authority, which makes the scheme impractical. Second, they are insecure against collusion attacks. Finally, only queries from the same domain (intra-domain) are considered. We note that one of the main applications of identity-based proxy re-encryption schemes is in the cloud computing scenario. Nevertheless, in this scenario, users in different domains can share files with each other. Therefore, the existing solutions do not actually solve the motivating scenario, when the scheme is applicable for cloud computing. Hence, it remains an interesting and challenging research problem to design an identity-based data storage scheme which is secure against collusion attacks and supports intra-domain and inter-domain queries. In this paper, we propose an identity-based data storage scheme where both queries from the intra-domain and inter-domain are considered and collusion attacks can be resisted. Furthermore, the access permission can be determined by the owner independently. © 2012 Elsevier B.V. All rights reserved

    LLL for ideal lattices re-evaluation of the security of Gentry-Halevi\u27s FHE scheme

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    The LLL algorithm, named after its inventors, Lenstra, Lenstra and Lovász, is one of themost popular lattice reduction algorithms in the literature. In this paper, we propose the first variant of LLL algorithm that is dedicated for ideal lattices, namely, the iLLL algorithm. Our iLLL algorithm takes advantage of the fact that within LLL procedures, previously reduced vectors can be re-used for further reductions. Using this method, we prove that the iLLL is at least as fast as the LLL algorithm, and it outputs a basis with the same quality. We also provide a heuristic approach that accelerates the re-use method. As a result, in practice, our algorithm can be approximately eight times faster than LLL algorithm for typical scenarios where lattice dimension is between 100 and 150. When applying our algorithm to the Gentry–Halevi’s fully homomorphic challenges, we are able to solve the toy challenge within 24 days using a 2.66GHz CPU, while with the classical LLL algorithm, it takes 32 days. Further, assuming a 4.0GHz CPU, we predict to reduce the basis in 15.7 years for the small challenges, while previous best prediction was 45 years

    On the Internal Structure of ALPHA-MAC

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    ALPHA-MAC is a MAC function which uses the building blocks of AES. This paper studies the internal structure of this new design. First, we provide a method to find second preimages based on the assumption that a key or an intermediate value is known. The proposed searching algorithm exploits the algebraic properties of the underlying block cipher and needs to solve eight groups of linear functions to find a second preimage. Second, we show that our idea can also be used to find internal collisions under the same assumption. We do not make any claims that those findings in any way endanger the security of this MAC function. Our contribution is showing how algebraic properties of AES can be used for analysis of this MAC function

    Generalized closest substring encryption

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    We propose a new cryptographic notion called generalized closest substring encryption. In this notion, a ciphertext encrypted with a string S can be decrypted with a private key of another string S′, if there exist a substring of S, i.e. S^, and a substring of S′, i.e. S^′, that are close to each other measured by their overlap distance . The overlap distance between S^ and S^′ is the number of identical positions at which the corresponding symbols are the same. In comparison with other encryption systems, the closest notion is the Fuzzy-IBE proposed by Sahai and Waters. The main difference is that the Fuzzy-IBE measures the overlap distance between S and S′, while ours measures the overlap distance of all of their substrings (including the complete string), and we take the maximum value among those. The overlap distance between their substrings will measure the similarity of S and S′ more precisely compared to the overlap distance between the two complete strings. We note that embedding this overlap distance in an encryption is a challenging task, in particular in order to achieve a practical scheme. Therefore, we invent a new approach to develop a practical generalized closest substring encryption system. The novelty of our approach relies on the way we generate ciphertext and private key representing the complete string so that they can still measure the overlap distance of substrings. The size of ciphertext and private key grow linearly only in the length of the input string. We prove the security in the selective model under a generalization of decision q-Bilinear Diffie-Hellman Exponent assumption

    Secure and anonymous mobile ad-hoc networks

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    A mobile ad-hoc network (MANET) is a wireless network made up of mobile hosts that do not require any fixed infrastructure to communicate. The major features of ad-hoc networks is self-organization and dynamics in user participation. Because of these features, the security in ad-hoc becomes a challenge. In this paper, we consider an interesting scenario, where an arbitrary number of nodes in MANET can dynamically form an anonymous group that exhibits the following features: (1) any outsider can be convinced that the node is indeed in the group; (2) any outsider can send a message back to the node in the group

    Improved identity-based online/offline encryption

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    The notion of online/offline encryption was put forth by Guo, Mu and Chen (FC 2008), where they proposed an identity-based scheme called identity-based online/offline encryption (IBOOE). An online/ offline encryption separates an encryption into two stages: offline and online. The offline phase carries much more computational load than the online phase, where the offline phase does not require the information of the message to be encrypted and the identity of the receiver. Subsequently, many applications of IBOOE have been proposed in the literature. As an example, Hobenberger and Waters (PKC 2014) have recently applied it to attribute-based encryption. In this paper, we move one step further and explore a much more efficient variant.We propose an efficient semi-generic transformation to obtain an online/offline encryption from a tradition identity-based encryption (IBE). Our transformation provides a new method to separate the computation of receiver’s identity into offline and online phases. The IBOOE schemes using our transformation saves one group element in both offline and online phases compared to other IBOOE schemes in identity computing. The transformed scheme still maintains the same level of security as in the original IBE scheme

    Privacy-Preserving Mutual Authentication in RFID with Designated Readers

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    We study privacy-preserving mutual authentication in radio-frequency identification systems with designated readers (PP-MADR in short). In PP-MADR, each tag has its designated-reader group instead of all readers, and only tags and their designated readers can authenticate each other. Other readers and adversaries cannot trace tags or know their designated readers. The most challenging task of constructing such a PP-MADR protocol is the verification of reader designation without compromising tag privacy. We found that traditional solutions are impractical due to linear storage growth on tags, linear computation growth on tags, or requiring new key generations for designated readers. In this paper, we show how to construct such an efficient PP-MADR protocol. In our protocol, each tag stores constant-size secret state and performs constant-time computation for mutual authentication. When a tag is created, the server does not generate new private keys for designated readers. Our protocol captures the strong privacy property, where tags cannot be traced and designated readers cannot be distinguished, even if tags are corrupted by adversaries

    On the security of text-based 3D CAPTCHAs

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    CAPTCHAs have become a standard security mechanism that are used to deter automated abuse of online services intended for humans. However, many existing CAPTCHA schemes to date have been successfully broken. As such, a number of CAPTCHA developers have explored alternative methods of designing CAPTCHAs. 3D CAPTCHAs is a design alternative that has been proposed to overcome the limitations of traditional CAPTCHAs. These CAPTCHAs are designed to capitalize on the human visual system\u27s natural ability to perceive 3D objects from an image. The underlying security assumption is that it is difficult for a computer program to identify the 3D content. This paper investigates the robustness of text-based 3D CAPTCHAs. In particular, we examine three existing text-based 3D CAPTCHA schemes that are currently deployed on a number of websites. While the direct use of Optical Character Recognition (OCR) software is unable to correctly solve these textbased 3D CAPTCHA challenges, we highlight certain patterns in the 3D CAPTCHAs can be exploited to identify important information within the CAPTCHA. By extracting this information, this paper demonstrates that automated attacks can be used to solve these 3D CAPTCHAs with a high degree of success
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