The Bitcoin Backbone Protocol: Analysis and Applications

Garay, Juan A.; Kiayias, Aggelos; Leonardos, Nikos

doi:10.1007/978-3-662-46803-6_10

Cited by 1,045 publications

(1,270 citation statements)

References 24 publications

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“…Implementing a consistent bulletin board is beyond our scope, however we note that it can be achieved in the standard model using Byzantine agrement (BA) (for BA, see e.g., [26]) by assuming secure channels between any pair of parties. In fact, recently, it is shown that one can achieve BA efficiently even without secure channels in a completely anonymous setting [27] hence removing the requirement for pairwise secure channels (but note that this latter work relies on proofs of work modeled in the RO model). Why previously known techniques do not work.…”

Section: Introductionmentioning

confidence: 99%

End-to-End Verifiable Elections in the Standard Model

Kiayias

Zacharias

Zhang

2015

Advances in Cryptology - EUROCRYPT 2015

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123

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We present the cryptographic implementation of "DEMOS", a new e-voting system that is endto-end verifiable in the standard model, i.e., without any additional "setup" assumption or access to a random oracle (RO). Previously known end-to-end verifiable e-voting systems required such additional assumptions (specifically, either the existence of a "randomness beacon" or were only shown secure in the RO model). In order to analyze our scheme, we also provide a modeling of endto-end verifiability as well as privacy and receipt-freeness that encompasses previous definitions in the form of two concise attack games.Our scheme satisfies end-to-end verifiability information theoretically in the standard model and privacy/receipt-freeness under a computational assumption (subexponential Decisional Diffie Helman). In our construction, we utilize a number of techniques used for the first time in the context of e-voting schemes that include utilizing randomness from bit-fixing sources, zero-knowledge proofs with imperfect verifier randomness and complexity leveraging.

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Section: Introductionmentioning

confidence: 99%

End-to-End Verifiable Elections in the Standard Model

Kiayias

Zacharias

Zhang

2015

Advances in Cryptology - EUROCRYPT 2015

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123

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“…As in Garay et al's formal analysis of the Bitcoin backbone protocol [GKL15], the problem is made tractable by assuming that communications over the network are instantaneous. Honest miners are always working with the longest blockchain that they know of, and the broadcast messages are always received by all the miners.…”

Section: Game Modelmentioning

confidence: 99%

“…Relevant values for the delay ∆ can be deduced from the analysis performed in [GKL15] where the authors evaluate the probability to have a fork of two branches of a given length. From a practical point of view, a look back to the history of broadcast Bitcoin blocks permits to find all the accidental forks that have ever been observed.…”

Section: Relevant Values For ∆mentioning

confidence: 99%

Malleability of the blockchain’s entropy

Pierrot

Wesolowski

2017

Cryptogr. Commun.

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Abstract. Trustworthy generation of public random numbers is necessary for the security of a number of cryptographic applications. It was suggested to use the inherent unpredictability of blockchains as a source of public randomness. Entropy from the Bitcoin blockchain in particular has been used in lotteries and has been suggested for a number of other applications ranging from smart contracts to election auditing. In this Arcticle, we analyse this idea and show how an adversary could manipulate these random numbers, even with limited computational power and financial budget.

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“…Under certain assumptions about the network synchronicity and the hardness of the proof, the above mechanism has been shown to be robust in the sense of satisfying two properties, persistence (transactions remain stable in the "ledger") and liveness (all transactions are eventually inserted in the ledger) assuming that the honest parties are above majority [GKL15]. Puzzle-based cryptocurrencies have also drawn a lot of criticism due to the fact that they require a lot of natural resources (e.g., in [OM14] it is reported that Bitcoin mining in 2014 already consumed as much energy as the needs of the country of Ireland for electricity).…”

Section: Powork-based Cryptocurrenciesmentioning

confidence: 99%

“…The formal statement and proof of the theorem (that should also include a formalization of all relevant underlying properties of cryptocurrencies, both in the puzzle-based and knowledgebased setting, e.g., in the sense of [GKL15]) is out of scope for the present exposition.…”

Section: Powork-based Cryptocurrenciesmentioning

confidence: 99%

Indistinguishable Proofs of Work or Knowledge

Baldimtsi

Kiayias

Zacharias

et al. 2016

Advances in Cryptology – ASIACRYPT 2016

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We introduce a new class of protocols called Proofs of Work or Knowledge (PoWorKs). In a PoWorK, a prover can convince a verifier that she has either performed work or that she possesses knowledge of a witness to a public statement without the verifier being able to distinguish which of the two has taken place. We formalize PoWorK in terms of three properties, completeness, f -soundness and indistinguishability (where f is a function that determines the tightness of the proof of work aspect) and present a construction that transforms 3-move HVZK protocols into 3-move public-coin PoWorKs. To formalize the work aspect in a PoWorK protocol we define cryptographic puzzles that adhere to certain uniformity conditions, which may also be of independent interest. We instantiate our puzzles in the random oracle (RO) model as well as via constructing "dense" versions of suitably hard one-way functions.We then showcase PoWorK protocols by presenting a number of applications. We first show how non-interactive PoWorKs can be used to reduce spam email by forcing users sending an e-mail to either prove to the mail server they are approved contacts of the recipient or to perform computational work. As opposed to previous approaches that applied proofs of work to this problem, our proposal of using PoWorKs is privacy-preserving as it hides the list of the receiver's approved contacts from the mail server. Our second application, shows how PoWorK can be used to compose cryptocurrencies that are based on proofs of work ("Bitcoin-like") with cryptocurrencies that are based on knowledge relations (these include cryptocurrencies that are based on "proof of stake", and others). The resulting PoWorK-based cryptocurrency inherits the robustness properties of the underlying two systems while PoWorK-indistinguishability ensures a uniform population of miners. Finally, we show that PoWorK protocols imply straight-line quasi-polynomial simulatable arguments of knowledge and based on our construction we obtain an efficient straight-line concurrent 3-move statistically quasi-polynomial simulatable argument of knowledge.

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The Bitcoin Backbone Protocol: Analysis and Applications

Cited by 1,045 publications

References 24 publications

End-to-End Verifiable Elections in the Standard Model

End-to-End Verifiable Elections in the Standard Model

Malleability of the blockchain’s entropy

Indistinguishable Proofs of Work or Knowledge

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