Abstract. In data publishing, the owner delegates the role of satisfying user queries to a third-party publisher. As the publisher may be untrusted or susceptible to attacks, it could produce incorrect query results. This paper introduces a mechanism for users to verify that their query answers on a multi-dimensional dataset are correct, in the sense of being complete (i.e., no qualifying data points are omitted) and authentic (i.e., all the result values originated from the owner). Our approach is to add authentication information into a spatial data structure, by constructing certified chains on the points within each partition, as well as on all the partitions in the data space. Given a query, we generate proof that every data point within those intervals of the certified chains that overlap the query window either is returned as a result value, or fails to meet some query condition. We study two instantiations of the approach: Verifiable KD-tree (VKDtree) that is based on space partitioning, and Verifiable R-tree (VRtree) that is based on data partitioning. The schemes are evaluated on window queries, and results show that VRtree is highly precise, meaning that few data points outside of a query result are disclosed in the course of proving its correctness.
Cu-based tandem nanocrystals have been widely applied to produce multicarbon (C 2+ ) products via enhancing CO intermediate (*CO) coverage toward CO 2 electroreduction. Nevertheless, it remains ambiguous to understand the intrinsic correlation between *CO coverage and C−C coupling. Herein, we constructed a tandem catalyst via coupling CoPc with the gas diffusion electrode of Cu (GDE of Cu−CoPc). A faradaic efficiency for C 2+ products of 82% was achieved over a GDE of Cu−CoPc at an applied current density of 480 mA cm −2 toward CO 2 electroreduction, which was 1.8 times as high as that over the GDE of Cu. Based on in situ experiments and density functional theory calculations, we revealed that the high *CO coverage induced by CO-generating CoPc promoted the local enrichment of *CO with the top adsorption mode, thus reducing the energy barrier for the formation of OCCO intermediate. This work provides an in-depth understanding of the surface coverage-dependent mode-specific C−C coupling mechanism toward CO 2 electroreduction.
In data outsourcing model, data owners engage third-party data servers (called publishers) to manage their data and process queries on their behalf. As these publishers may be untrusted or susceptible to attacks, it could produce incorrect query results to users. In this paper, we introduce an authentication scheme for outsourced multi-dimensional databases. With the proposed scheme, users can verify that their query answers from a publisher are complete (i.e., no qualifying tuples are omitted) and authentic (i.e., all the result values are legitimate). In addition, our scheme guarantees minimality (i.e., no nonanswer points are returned in the plain). Our scheme supports window, range, kNN and RNN queries on multi-dimensional databases. We have implemented the proposed scheme, and our experimental results on kNN queries show that our approach is a practical scheme with low overhead.
-In the database outsourcing paradigm, a data owner (DO) delegates its DBMS administration to a specialized service provider (SP) that receives and processes queries from clients. The traditional outsourcing model (TOM) requires that the DO and the SP maintain authenticated data structures to enable authentication of query results. In this paper, we present SAE, a novel outsourcing model that separates authentication from query execution. Specifically, the DO does not perform any task except for maintaining its dataset (if there are updates). The SP only stores the DO's dataset and computes the query results using a conventional DBMS. All security-related tasks are outsourced to a separate trusted entity (TE), which maintains limited authentication information about the original dataset. A client contacts the TE when it wishes to establish the correctness of a result returned by the SP. The TE efficiently generates a verification token of negligible size. The client can verify the token with minimal cost. SAE eliminates the participation of the DO and the SP in the authentication process, and outperforms TOM in every aspect, including processing cost for all parties involved, communication overhead, query response time and ease of implementation in practical applications. I. INTRODUCTIONInstead of administrating their data locally, several organizations outsource DBMS management to third-party service providers that receive and process queries from clients. The providers are not necessarily trustworthy and, thus, they should be able to prove that the results are sound (i.e., unaltered and containing no bogus data) and complete (i.e., all records satisfying the query are present). We refer to a sound and complete query result as correct. Figure 1 illustrates the traditional outsourcing model (TOM). The data owner (DO) builds an authenticated data structure (ADS) over its dataset. The ADS is a conventional index, augmented with hash values or signatures generated with a public-key cryptosystem (e.g., RSA). The DO transmits its dataset and signatures to the service provider (SP), which constructs the ADS locally and utilizes it to compute the result of each incoming query, as well as a verification object (VO). The VO contains authentication data (i.e., hashes/signatures) for proving the correctness of the query result. In case of updates, the DO generates new signatures, modifies its ADS, and notifies the SP that updates its ADS accordingly.
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