Abstract Ad exchanges are kind of the most popular online advertising marketplaces for trading ad spaces over the Internet. Ad exchanges run auctions to sell diverse ad spaces on the publishers’ web-pages to advertisers, who want to display ads on ad spaces. However, the parties in an ad auction cannot verify whether the auction is carried out correctly or not. Furthermore, the advertisers are usually unwilling to reveal their sensitive bids and identities. In this paper, we jointly consider the auction verifiability and the advertisers’ privacy preservation, and thus propose ERA, which is an E fficient, p R ivacy-preserving, and verifi A ble online auction mechanism for ad exchanges. ERA exploits an order preserving encryption scheme to guarantee privacy preservation, and achieves verifiability by constructing a novel protocol of privacy preserving integer comparison, which is built on the Paillier homomorphic encryption scheme. We extensively evaluate the performance of ERA, and our evaluation results show that ERA satisfies several desirable properties with low computation, communication, and storage overheads, so ERA can be easily deployed in today's ad exchanges.
: A third party is introduced to cooperate with the auctioneer to run the auctions. The scheme proposed by Naor in @cite_19 constructed a boolean circuit, which calculates the auction outcome for any given set of bids. Based on RSA, Juels and Szydlo proposed a privacy preserving auction mechanism with a reasonable computational complexity @cite_16 . Specific to online applications, a number of auction mechanisms @cite_30 @cite_41 @cite_2 get a good tradeoff between performance and security. Unfortunately, these works only consider bid protection, but ignore the problem of verification. ERA belongs to this category, and moves forwards to guarantee verifiability and privacy preservation at the same time.
@cite_30 @cite_41 @cite_19 @cite_2 @cite_16
1599852298 1993116423 2950920780 2951660602
Naor, Pinkas, and Sumner introduced and implemented a sealed-bid, two-server auction system that is perhaps the most efficient and practical to date. Based on a cryptographic primitive known as oblivious transfer, their system aims to ensure privacy and correctness provided that at least one auction server behaves honestly. As observed in [19], however, the NPS system suffers from a security flaw in which one of the two servers can cheat so as to modify bids almost arbitrarily and without detection. We propose a means of repairing this flaw while preserving the attractive practical elements of the NPS protocol, including minimal round complexity for servers and minimal computation by players providing private inputs. Our proposal requires a slightly greater amount of computation and communication on the part of the two auction servers, but actually involves much less computation on the part of bidders. This latter feature makes our proposal particularly attractive for use with low-power devices. While the original proposal of NPS involved several dozen exponentiations for a typical auction, ours by contrast involves only several dozen modular multiplications. The key idea in our proposal is a form of oblivious transfer that we refer to as verifiable proxy oblimous transfer (VPOT). We study the role that privacy-preserving algorithms, which prevent the leakage of specific information about participants, can play in the design of mechanisms for strategic agents, which must encourage players to honestly report information. Specifically, we show that the recent notion of differential privacv, in addition to its own intrinsic virtue, can ensure that participants have limited effect on the outcome of the mechanism, and as a consequence have limited incentive to lie. More precisely, mechanisms with differential privacy are approximate dominant strategy under arbitrary player utility functions, are automatically resilient to coalitions, and easily allow repeatability. We study several special cases of the unlimited supply auction problem, providing new results for digital goods auctions, attribute auctions, and auctions with arbitrary structural constraints on the prices. As an important prelude to developing a privacy-preserving auction mechanism, we introduce and study a generalization of previous privacy work that accommodates the high sensitivity of the auction setting, where a single participant may dramatically alter the optimal fixed price, and a slight change in the offered price may take the revenue from optimal to zero. We study the communication complexity of combinatorial auctions via interpolation mechanisms that interpolate between non-truthful and truthful protocols. Specifically, an interpolation mechanism has two phases. In the first phase, the bidders participate in some non-truthful protocol whose output is itself a truthful protocol. In the second phase, the bidders participate in the truthful protocol selected during phase one. Note that virtually all existing auctions have either a non-existent first phase (and are therefore truthful mechanisms), or a non-existent second phase (and are therefore just traditional protocols, analyzed via the Price of Anarchy Stability). The goal of this paper is to understand the benefits of interpolation mechanisms versus truthful mechanisms or traditional protocols, and develop the necessary tools to formally study them. Interestingly, we exhibit settings where interpolation mechanisms greatly outperform the optimal traditional and truthful protocols. Yet, we also exhibit settings where interpolation mechanisms are provably no better than truthful ones. Finally, we apply our new machinery to prove that the recent single-bid mechanism of Devanur et. al. DevanurMSW15 (the only pre-existing interpolation mechanism in the literature) achieves the optimal price of anarchy among a wide class of protocols, a claim that simply can't be addressed by appealing just to machinery from communication complexity or the study of truthful mechanisms. We study a central problem in Algorithmic Mechanism Design: constructing truthful mechanisms for welfare maximization in combinatorial auctions with submodular bidders. Dobzinski, Nisan, and Schapira provided the first mechanism that guarantees a non-trivial approximation ratio of @math [STOC'06], where @math is the number of items. This was subsequently improved to @math [Dobzinski, APPROX'07] and then to @math [Krysta and Vocking, ICALP'12]. In this paper we develop the first mechanism that breaks the logarithmic barrier. Specifically, the mechanism provides an approximation ratio of @math . Similarly to previous constructions, our mechanism uses polynomially many value and demand queries, and in fact provides the same approximation ratio for the larger class of XOS (a.k.a. fractionally subadditive) valuations. We also develop a computationally efficient implementation of the mechanism for combinatorial auctions with budget additive bidders. Although in general computing a demand query is NP-hard for budget additive valuations, we observe that the specific form of demand queries that our mechanism uses can be efficiently computed when bidders are budget additive.