Timed Signatures and Zero-Knowledge Proofs: Timestamping in the Blockchain Era

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Timestamping is an important cryptographic primitive with numerous applications. The availability of a decentralized blockchain such as that offered by the Bitcoin protocol offers new possibilities to realise timestamping services. Even though there are blockchain-based timestamping proposals, they are not formally defined and proved in a universally composable (UC) setting. In this work, we put forth the first formal treatment of timestamping cryptographic primitives in the UC framework with respect to a global clock. We propose timed versions of primitives commonly used for authenticating information, such as digital signatures, non-interactive zero-knowledge proofs, and signatures of knowledge. We show how they can be UC-securely constructed by a protocol that makes ideal (blackbox) access to a transaction ledger. Our definitions introduce a fine-grained treatment of the different timestamping guarantees, namely security against postdating and backdating attacks; our results treat each of these cases separately and in combination, and shed light on the assumptions that they rely on. Our constructions rely on a relaxation of an ideal beacon functionality, which we construct UC-securely. Given many potential use cases of such a beacon in cryptographic protocols, this result is of independent interest.
Original languageEnglish
Title of host publicationApplied Cryptography and Network Security (ACNS 2020)
Subtitle of host publication18th International Conference, ACNS 2020, Rome, Italy, October 19–22, 2020, Proceedings, Part I
PublisherSpringer
Pages335 - 354
Number of pages20
ISBN (Electronic)978-3-030-57808-4
ISBN (Print)978-3-030-57807-7
DOIs
Publication statusPublished - 27 Aug 2020
Event18th International Conference on Applied Cryptography and Network Security - Rome, Italy
Duration: 19 Oct 202022 Oct 2020
https://sites.google.com/di.uniroma1.it/ACNS2020

Publication series

NameLecture Notes in Computer Science
PublisherSpringer
Volume12146
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference18th International Conference on Applied Cryptography and Network Security
Abbreviated titleACNS 2020
CountryItaly
CityRome
Period19/10/2022/10/20
Internet address

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