Generic Fully Simulatable Adaptive Oblivious Transfer

In this paper, we provide the first scheme that realises an attribute-based access control system for static resources that offers maximal privacy and is secure in the universal composability framework (UC). More precisely, we offer a protocol for adaptive oblivious transfer, where the sender can enforce an attribute-based access control policy for each record and nevertheless learns neither which record a user retrieves nor which attributes a user has. As additional results we provide a new structure-preserving signature scheme from the SXDH assumption and a new universally composable adaptive oblivious transfer protocol that is secure under two DDH-like assumptions and is the most efficient one secure under ``non $q$-type'' assumptions. We believe the new signature scheme to be of independent interest as a building block that is compatible with Groth-Sahai non-interactive zero-knowledge proofs.

We propose an efficient adaptive oblivious transfer protocol with hidden access policies. This scheme allows a receiver to anonymously recover a message from a database which is protected by hidden attribute based access policy if the receiver's attribute set satisfies the associated access policy implicitly. The proposed scheme is secure in the presence of malicious adversary under the q-Strong Diffie-Hellman (SDH), q-Power Decisional Diffie-Hellman (PDDH) and Decision Bilinear Diffie-Hellman (DBDH) assumption in full-simulation security model. The scheme covers disjunction of attributes. The proposed protocol outperforms the existing similar schemes in terms of both communication and computation.

In order to guarantee a fair and transparent voting process, electronic voting schemes must be verifiable. Most of the time, however, it is important that elections also be anonymous. The notion of a verifiable shuffle describes how to satisfy both properties at the same time: ballots are submitted to a public bulletin board in encrypted form, verifiably shuffled by several mix servers (thus guaranteeing anonymity), and then verifiably decrypted by an appropriate threshold decryption mechanism. To guarantee transparency, the intermediate shuffles and decryption results, together with proofs of their correctness, are posted on the bulletin board throughout this process.In this paper, we present a verifiable shuffle and threshold decryption scheme in which, for security parameter k, L voters, M mix servers, and N decryption servers, the proof that the end tally corresponds to the original encrypted ballots is only O(k(L + M + N)) bits long. Previous verifiable shuffle constructions had proofs of size O(kLM + kLN), which, for elections with thousands of voters, mix servers, and decryption servers, meant that verifying an election on an ordinary computer in a reasonable amount of time was out of the question.The linchpin of each construction is a controlled-malleable proof (cm- NIZK), which allows each server, in turn, to take a current set of ciphertexts and a proof that the computation done by other servers has proceeded correctly so far. After shuffling or partially decrypting these ciphertexts, the server can also update the proof of correctness, obtaining as a result a cumulative proof that the computation is correct so far. In order to verify the end result, it is therefore sufficient to verify just the proof produced by the last server.KeywordsProof SystemBulletin BoardCommitment SchemeCryptology ePrint ArchiveCommon Reference StringThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Adaptive Oblivious Transfer Protocol with Hidden Access Policy (AOT-HAP) is a well known cryptographic primitive that combines each message of a database with an access policy which is kept hidden. The database is held by a sender who encrypts each message of the database under its access policy and publishes encrypted database in which access policies are embedded implicitly. A receiver possesses an attribute set and recovers the message correctly if the attribute set satisfies the access policy implicitly. Otherwise, a garbage message is recovered by the receiver. In this paper, an efficient \(\mathsf{AOT{\text {-}}HAP}\) is presented. The proposed protocol realizes more expressive access policies, i.e., conjunction as well as disjunction of attributes. The proposed \(\mathsf{AOT{\text {-}}HAP}\) is secure assuming the hardness of standard assumptions in the presence of malicious adversary in full-simulation security model. It exhibits significant improvement over the existing similar schemes in terms of both communication and computation.KeywordsOblivious transferAccess policyAttribute based encryptionFull simulation security model

Some novel effective 1-out-of-2, 1-out-of-n, n−1-out-of-n, andm-out-of-n interactive and non-interactive oblivious transfer protocols (OT protocols) using a probabilistic encryption are presented. Their key information is adapted from corresponding Bellare − Rivest fractional OT protocols and the encryption is carried out on ElGamal. They can be realized in a multiplicative as well as an additive group of prime order. It is shown that due to usage of different encryption keys this implementation can be simplified in such a way that single randomizer is sufficient for all encryptions. The proposal allows to increase the information rate by 2n/(n+1) times and to reduce by the same factor the computational complexity of the second round phase of interactive and of the communication phase of non-interactive m-out-of-n OT protocols explored probabilistic encryption. These propositions have potential applications in all cryptographic protocols based on the m-out-of-n oblivious transfer using probabilistic encryption including generalized oblivious transfer, in particular in electronic commerce.

In this paper we isolate a combinatorial problem that, we believe, lies at the heart of this question and provide some encouragingly positive solutions to it. We show that there exists an N-processor realistic computer that can simulate arbitrary idealistic N-processor parallel computations with only a factor of O(log N) loss of runtime efficiency. The main innovation is an O(log N) time randomized routing algorithm. Previous approaches were based on sorting or permutation networks, and implied loss factors of order at least (log N)2.

Oblivious transfer (OT) is a primitive of great importance in two-party and multi-party computation. We introduce a general construction of universally composable (UC) oblivious transfer protocols based on lossy cryptosystems in the common reference string (CRS) model, yielding protocols under several assumptions. In order to achieve this, we show that for most known lossy encryption constructions it is possible to distinguish between lossy and injective public keys given the corresponding secret key, similarly to dual-mode encryption in messy mode. Furthermore, we adapt the techniques of our general construction to obtain the first UC secure OT protocol based on the McEliece assumptions, which are coding theory based assumptions that until now have resisted quantum attacks, thus introducing the first UC secure OT protocol based on coding assumptions. However, differently from previous results based on dual-mode encryption, our scheme does not require a trapdoor for opening lossy ciphertexts, relying instead on CRS manipulation and cut-and-choose techniques to construct the simulators. In both constructions we circumvent the need for universally composable string commitment schemes, which are required by previous black-box compilers.

Researchers face a tradeoff when applying latent variable models to time-series, cross-sectional data. Static models minimize bias but assume data are temporally independent, resulting in a loss of efficiency. Dynamic models explicitly model temporal data structures, but smooth estimates of the latent trait across time, resulting in bias when the latent trait changes rapidly. We address this tradeoff by investigating a new approach for modeling and evaluating latent variable estimates: a robust dynamic model. The robust model is capable of minimizing bias and accommodating volatile changes in the latent trait. Simulations demonstrate that the robust model outperforms other models when the underlying latent trait is subject to rapid change, and is equivalent to the dynamic model in the absence of volatility. We reproduce latent estimates from studies of judicial ideology and democracy. For judicial ideology, the robust model uncovers shocks in judicial voting patterns that were not previously identified in the dynamic model. For democracy, the robust model provides more precise estimates of sudden institutional changes such as the imposition of martial law in the Philippines (1972–1981) and the short-lived Saur Revolution in Afghanistan (1978). Overall, the robust model is a useful alternative to the standard dynamic model for modeling latent traits that change rapidly over time.

We propose a new test of linkage in the presence of allelic association that uses all available information in a sample of nuclear families, including parental phenotypes, genotypes from both affected and unaffected siblings, and families with homozygous parents. The test is based on the conditional framework developed by Rabinowitz and Laird [2000: Hum Hered 50:211-223] and is thus immune to population stratification and can be applied to families with any pattern of missing information. The test statistic is a conditional likelihood ratio based on a standard two-point linkage model with allelic association, where parameters are estimated from the sample. Through a simulation study, we determined that the proposed test has near optimal power for a wide range of scenarios, outperforming FBAT both when data were complete and when parental genotypes were missing, although differences between the two tests diminish as the genetic effect is reduced. To assess robustness, we also evaluated the performance of the tests under scenarios with population stratification and found that although there is a loss of efficiency, our proposed test remains a strong competitor to FBAT.

With the rapid development of the power Internet of Things, more and more intelligent terminals in the power scene need to interact with users for information. Building a standard information physical model to realize the unified access of multi-source and heterogeneous terminals is a major problem faced by the construction of the electric Internet of Things. Based on MQTT's good adaptability to the Internet of Things and Docker's cross-platform, this paper designs a system for adaptive conversion of power distribution protocol based on the Internet of Things management platform. Firstly, the frame structure of distribution specification is analyzed and the process of protocol adaptive recognition and analysis adopted by the system is explained. Then, it describes the interaction function of the cloud controller and the side controller docking Roma platform and Docker engine, analyzes the call method of Roma platform based on HPPTS protocol to the north API and Docker API, and explains the Pub/Sub model based on MQTT protocol. And how the platform and devices communicate based on a custom Topic. The cloud edge interaction between controller and controller completes the interface call and system implementation of adaptive protocol transformation. It has completed the test and verification of the adaptive conversion system of power distribution protocol in Hunan Communication Laboratory, which provides an open IoT platform for the power IoT system of Hunan Province, and provides important guidance for the construction of a set of intelligent cloud edge system in Hunan Province. It is of great significance for the construction and promotion of the power IoT system of Hunan Province.

Adaptive hypertext transfer protocol (HTTP) streaming has become a new trend to support adaptivity in video delivery. An HTTP streaming client needs to estimate exactly resource availability and resource demand. In this paper, we focus on the most important resource which is bandwidth. A new and general formulation for throughput estimation is presented taking into account previous values of instant throughput and round trip time. Besides, we introduce for the first time the use of bitrate estimation in HTTP streaming. The experiments show that our approach can effectively cope with drastic changes in connection throughput and video bitrate.

For nearly a decade, observations have shown that many older Sun-like stars spin faster than predicted, a phenomenon known as weakened magnetic braking (WMB). The leading hypothesis for WMB is a weakening of the large-scale dipole field, which leads to a less efficient angular momentum loss. To test this hypothesis on a star known to be in the WMB regime, we present the first Zeeman Doppler imaging (ZDI) map of the Sun-like star τ Ceti, reconstructed using spectropolarimetric data from the Canada–France–Hawai‘i Telescope. Our ZDI analysis reveals a remarkably simple, stable, and weak (〈B〉 = 0.17 G) magnetic field, characterized by a predominantly dipolar (∼92% magnetic energy contained in l = 1 modes), and highly axisymmetric (∼88% magnetic energy contained in m < l/2 modes) morphology. We infer a dipole field strength of B dip = 0.31 G, nearly an order of magnitude weaker than standard braking model predictions, providing direct confirmation of the weakened large-scale dipole predicted by the WMB hypothesis. This work establishes a new benchmark for ZDI, demonstrating that even extremely quiet stars in the WMB regime are accessible to this technique.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Tomonori Totani; Very high energy phenomena in GRBs. AIP Conf. Proc. 23 March 2001; 556 (1): 221–227. https://doi.org/10.1063/1.1368279 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

We explore the security of blind signatures under aborts where the user or the signer may stop the interactive signature issue protocol prematurely. Several works on blind signatures discuss security only in regard of completed executions and usually do not impose strong security requirements in case of aborts. One of the exceptions is the paper of Camenisch, Neven and shelat (Eurocrypt 2007) where the notion of selective-failure blindness has been introduced. Roughly speaking, selective-failure blindness says that blindness should also hold in case the signer is able to learn that some executions have aborted. Here we augment the work of Camenisch et al. by showing how to turn every secure blind signa- ture scheme into a selective-failure blind signature scheme. Our transformation only requires an additional computation of a commitment and therefore adds only a negligible overhead. We also study the case of multiple executions and notions of selective-failure blindness in this setting. We then discuss the case of user aborts and unforgeability under such aborts. We show that every three-move blind signature scheme remains unforgeable under such user aborts. Together with our transformation for selective-failure blindness we thus obtain an easy solution to ensure security under aborts of either party and which is applicable for example to the schemes of Pointcheval and Stern (Journal of Cryptology, 2000). We

In Asiacrypt’08, Green and Hohenberger presented an adaptive oblivious transfer (OT) scheme which makes use of a signature built from the Boneh-Boyen Identity Based Encryption. In this note, we show that the signature scheme is vulnerable to known-message attacks and the reduction used in the proof of Lemma A.6 is flawed. We also remark that the paradigm of “encryption and proof of knowledge” adopted in the OT scheme is unnecessary because the transferred message must be “recognizable” in practice, otherwise the receiver cannot decide which message to retrieve. However, we would like to stress that this work does not break the OT scheme itself.