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Black-Box Wallets: Fast Anonymous Two-Way Payments for Constrained Devices

Hoffmann, Max; Klooß, Michael; Raiber, Markus; Rupp, Andy

Abstract (englisch):
Black-box accumulation (BBA) is a building block which enables a privacy-preserving implementation of point collection and redemption, a functionality required in a variety of user-centric applications including loyalty programs, incentive systems, and mobile payments. By definition, BBA+ schemes (Hartung et al. CCS '17) offer strong privacy and security guarantees, such as unlinkability of transactions and correctness of the balance flows of all (even malicious) users. Unfortunately, the instantiation of BBA+ presented at CCS '17 is, on modern smartphones, just fast enough for comfortable use. It is too slow for wearables, let alone smart-cards. Moreover, it lacks a crucial property: For the sake of efficiency, the user's balance is presented in the clear when points are deducted. This may allow to track owners by just observing revealed balances, even though privacy is otherwise guaranteed. The authors intentionally forgo the use of costly range proofs, which would remedy this problem.

We present an instantiation of BBA+ with some extensions following a different technical approach which significantly improves efficiency. To this end, we get rid of pairing groups, rely on different zero-knowledge and fast range proofs, along with a slightly modified version of Baldimtsi-Lysyanskaya blind signatures (CCS '13). ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000122242/pub
Veröffentlicht am 29.07.2020
DOI: 10.2478/popets-2020-0010
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Theoretische Informatik (ITI)
Kompetenzzentrum für angewandte Sicherheitstechnologie (KASTEL)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 01.2020
Sprache Englisch
Identifikator ISSN: 2299-0984
KITopen-ID: 1000122242
Erschienen in Proceedings on privacy enhancing technologies
Verlag De Gruyter
Band 2020
Heft 1
Seiten 165–194
Vorab online veröffentlicht am 07.01.2020
Schlagwörter cryptographic protocols / anonymity, discrete logarithm problem, electronic commerce and payment, elliptic curve cryptosystem, implementation, smart cards, mobile payments, customer loyalty programs, incentive systems, black-box accummulation
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