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9,005 results · page 295 of 376
Sourav Das, Aashish Kolluri, Prateek Saxena, Haifeng Yu
No abstract is available for this record.
Fengjun Chen, Zhiqiang Liu, Long Yu, Zhen Liu · 5 authors
No abstract is available for this record.
Ning Zhang, Jin Li, Wenjing Lou, Yongchao Hou
No abstract is available for this record.
Songjie Wei, Shuai Li, Peilong Liu, Meilin Liu
LEO constellation has received intensive research attention in the field of satellite communication. The existing centralized authentication protocols traditionally used for MEO/GEO satellite networks cannot accommodate LEO satellites with frequent user connection switching. This paper proposes a fast and efficient access verification protocol named BAVP by combining identity-based encryption and blockchain technology. Two different key management schemes with IBE and blockchain, respectively, are investigated, which further enhance the authentication reliability and efficiency in LEO constellation. Experiments on OPNET simulation platform evaluate and demonstrate the effectiveness, reliability, and fast-switching efficiency of the proposed protocol. For LEO networks, BAVP surpasses the well-known existing solutions with significant advantages in both performance and scalability which are supported by theoretical analysis and simulation results.
Leonardo Aniello, Roberto Baldoni, Federico Lombardi
No abstract is available for this record.
Yingjie Gu, Xiaolin Gui, Pan Xu, Ruowei Gui · 6 authors
No abstract is available for this record.
Asma Alnemari, Suchith Arodi, Valentina Rodriguez Sosa, Soni Pandey · 7 authors
No abstract is available for this record.
Jingyi Li, Jigang Wu, Long Chen, Jiaxing Li
No abstract is available for this record.
Georg Bramm, Mark Gall, Julian Schütte
No abstract is available for this record.
Hamza Abusalah
A proof system is a protocol between a prover and a verifier over a common input in which an honest prover convinces the verifier of the validity of true statements. Motivated by the success of decentralized cryptocurrencies, exemplified by Bitcoin, the focus of this thesis will be on proof systems which found applications in some sustainable alternatives to Bitcoin, such as the Spacemint and Chia cryptocurrencies. In particular, we focus on proofs of space and proofs of sequential work. Proofs of space (PoSpace) were suggested as more ecological, economical, and egalitarian alternative to the energy-wasteful proof-of-work mining of Bitcoin. However, the state-of-the-art constructions of PoSpace are based on sophisticated graph pebbling lower bounds, and are therefore complex. Moreover, when these PoSpace are used in cryptocur- rencies like Spacemint, miners can only start mining after ensuring that a commitment to their space is already added in a special transaction to the blockchain. Proofs of sequential work (PoSW) are proof systems in which a prover, upon receiving a statement χ and a time parameter T, computes a proof which convinces the verifier that T time units had passed since χ was received. Whereas Spacemint assumes synchrony to retain some interesting Bitcoin dynamics, Chia requires PoSW with unique proofs, i.e., PoSW in which it is hard to come up with more than one accepting proof for any true statement. In this thesis we construct simple and practically-efficient PoSpace and PoSW. When using our PoSpace in cryptocurrencies, miners can start mining on the fly, like in Bitcoin, and unlike current constructions of PoSW, which either achieve efficient verification of sequential work, or faster-than-recomputing verification of correctness of proofs, but not both at the same time, ours achieve the best of these two worlds.
Gwan-Hwan Hwang, Po‐Han Chen, Chun-Hao Lu, Chun Chiu · 6 authors
No abstract is available for this record.
Bram Cohen, Krzysztof Pietrzak
No abstract is available for this record.
Xi Chen, Yun Liu, Yong Li, Changlu Lin
No abstract is available for this record.
Li, Chao, Palanisamy, Balaji
In the age of Big Data, enabling task scheduling while protecting users' privacy is critical for various decentralized applications in blockchain-based smart contract platforms. Such a privacy-preserving task scheduler requires the task input data to be secretly maintained until a prescribed task execution time and be automatically recorded into the blockchain to enabling the execution of the task at the execution time, even if the user goes offline. While straight-forward centralized approaches provide a basic solution to the problem, unfortunately they are limited to a single point of trust and involve a single point of control. This paper presents decentralized techniques for supporting privacy-preserving task scheduling using smart contracts in Ethereum blockchain networks. We design a privacy-preserving task scheduling protocol that is managed by a manager smart contract. The protocol requires a user to schedule a task by deploying a proxy smart contract maintaining the non-sensitive information of the task while creating decentralized secret trust and selecting trustees from the network to maintain the sensitive information of the task. With security techniques including secret sharing and layered encryption as well as security deposit paid by trustees as economic deterrence, the protocol can protect the sensitive information against possible attacks including some trustees destroying the sensitive information (drop attack) or secretly releasing the sensitive information before the execution time (release-ahead attack). We demonstrate the attack-resilience of the proposed protocol through rigorous analysis.Our implementation and experimental evaluation on the Ethereum official test network demonstrate the low monetary cost and the low time overhead associated with the proposed approach.
Souradyuti Paul, Ananya Shrivastava
No abstract is available for this record.
Bo Zhao, Peiru Fan, Mingtao Ni
Virtual machine (VM) measurements data in IaaS cloud play a crucial role in integrity evaluation and decision making. Hence, the secure storage for these data has attracted more attention recently. This paper proposes a novel approach, named Mchain, to enhance the integrity and controllability of the secure storage. Especially, to enhance the integrity, a two-layer blockchain network is introduced. In the first layer, after the production, the data packages are first verified by leveraging a correspondence between a package and a policy, and a one-to-one relation among a VM, a user, and a node. After that, we propose a consensus achievement algorithm to construct a semi-finished block on a candidate block arranged by data packages. Meanwhile, the semi-finished block is distributed to all nodes, which can provide a certain integrity. In the second-layer, tamper-resistant metadata is generated by performing PoW tasks on the semi-finished block, resulting in strong integrity. Further, to enhance the controllability, a revisable user-defined policy-based encryption method with KP-ABE is proposed. It helps to flexibly control the scope of authorized verifiers. The experimental results on six scenarios with simulated data set show that the proposed approach is appealing in integrity and controllability, and the time overhead of data storage.
Takashi Yamakawa
Bilinear maps (also called pairings) have been used for constructing various kinds of cryptographic primitives including (but not limited to) short signatures, identity-based encryption, attribute-based encryption, and non-interactive zero-knowledge proof systems. In known instantiations of cryptographic bilinear maps based on eliptic curves, source and target groups are different groups, which may restrict applications of bilinear maps. Cheon and Lee studied self-bilinear maps, which are bilinear maps whose source and target groups are identical. They showed huge potential of self-bilinear maps by showing that self-bilinear maps can be transformed into multilinear maps, which give further more cryptographic applications including (but not limited to) multiparty non-interactive key exchange, broadcast encryption, attribute-based encryption, homomorphic signatures, and obfuscation. However, they also showed a strong negative result on the existence of cryptographic self-bilinear maps. Namely, they showed that if there exists an efficiently computable self-bilinear map on a known order group, then the computational Diffie-Hellman (CDH) assumption does not hold on the group. This means that cryptographically useful self-bilinear maps do not exist on groups of known order. On the other hand, there is no negative result for self-bilinear maps on groups of unknown order. Indeed, Yamakawa et al. gave a partial positive result for self-bilinear maps on unknown order groups. Namely, they constructed self-bilinear maps with auxiliary information, which is a weaker variant of self-bilinear maps based on indistinguishability obfuscation. Though they showed that they are sufficient for some applications of self-bilinear maps, they are not as useful as "ideal" self-bilinear maps, which do not need auxiliary information. In this talk, we first review the construction of self-bilinear maps with auxiliary information given by Yamakawa et al. Then we consider the possibility of constructing ideal self-bilinear maps.
Macià Mut–Puigserver, M. Magdalena Payeras–Capellà, Miquel À. Cabot-Nadal
No abstract is available for this record.
Victor C. Li
Digital identities and credentials are gradually replacing physical documents, as they can be verified with more accuracy and efficiency. Since online privacy is becoming more crucial than ever, it is essential to preserve the privacy of individuals whenever possible. Therefore, anonymous attestation of digital credentials should be feasible, where provers can selectively disclose attributes and create abstractions over attributes in their credential, in order to solely disclose the minimum amount of information required to complete the goal of verification.<br/><br/>Many schemes in the field of attribute-based credentials consider a single root authority issuing credentials to provers. This is coherent to the traditional way of the issuance of credentials since the process of producing physical documents is costly to distribute to multiple issuers. Digital identities provide the opportunity for authorities to distribute credential issuance rights (consecutively) to smaller entrusted entities.<br/><br/>To the best of our knowledge, we propose the first protocol which combines both anonymous attestation with attribute-based credentials and the delegation of selective signing rights for the issuance of these credentials. Root authorities could delegate signing rights for selective attributes consecutively to trustees, which are able to create anonymous attribute-based credentials with the acquired attributes for provers. Verifiers are able to verify presentation tokens with solely the public key of the root authority, without gaining knowledge about the identities of the prover and intermediate delegators. We introduce three adapted signature schemes based on existing work in order to realize a concrete instantiation of the protocol. Anonymity is achieved by incorporating Schnorr's zero-knowledge proof of knowledge with bilinear pairings to efficiently prove the correctness of presentation tokens.<br/><br/>We realized a prototype of our concrete instantiation and optimized the verification algorithm in order to achieve optimal pairing performance. Complexity analysis of the protocol shows improvement in efficiency by aggregating attribute signatures throughout signing right delegation. Experimental results demonstrate a degree of practical feasibility for the verification of presentation tokens on commodity hardware within the challenging public transportation access control time bound of 300 ms.<br/>
Jie Cai, Han Jiang, Qiuliang Xu, Guangshi Lv · 6 authors
No abstract is available for this record.
Constantin Cătălin Drăgan, Mark Manulis
No abstract is available for this record.
Maryline Laurent, Nesrine Kaaniche, Christian Le, Mathieu Vander Plaetse
International audience
Puwen Wei, Quan Yuan, Yuliang Zheng
No abstract is available for this record.
Esteban Landerreche, Marc Stevens
Recently we presented a single-party cryptographic timestamping mechanism based on proof-of-sequential-work, which we proved secure in the universal composability framework [16]. This paper describes this construction and its security claims and uses it to construct a multi-party permissioned blockchain protocol and show that it achieves an immutability notion. Finally we discuss applications of this protocol, including unpermissioned blockchains, and how these may benefit.