Paper 2019/644
Timed Signatures and Zero-Knowledge Proofs -Timestamping in the Blockchain Era-
Aydin Abadi and Michele Ciampi and Aggelos Kiayias and Vassilis Zikas
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. Nevertheless, to our knowledge, there are no recent blockchain-based proposals that are formally proved in a composable 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 refer to the corresponding primitives as timed to indicate this association. We propose timed versions of primitives commonly used for authenticating information, such as digital signatures, non-interactive zero-knowledge proofs, and signatures of knowledge and show how those can be UC-securely implemented by a protocol that makes ideal (blackbox) access to a global transaction ledger based on the ledger proposed by Badertscher et al. [CRYPTO 2017] which is UC realized by the Bitcoin backbone protocol [Eurocrypt 2015]. 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 implement UC-securely assuming the ledger functionality. Given the many potential uses of such a beacon in cryptographic protocols this result may be of independent interest.
Metadata
- Available format(s)
- Category
- Cryptographic protocols
- Publication info
- Preprint. MINOR revision.
- Keywords
- BlockchainDigital SignaturesZero-knowledge ProofsSignatures of KnowledgeUniversal Composability
- Contact author(s)
- aydin abadi @ ed ac uk,mciampi @ ed ac uk,akiayias @ inf ed ac uk,vassilis zikas @ ed ac uk
- History
- 2019-06-04: received
- Short URL
- https://ia.cr/2019/644
- License
-
CC BY