Paper 2016/991

Bootstrapping the Blockchain, with Applications to Consensus and Fast PKI Setup

Juan A. Garay, Aggelos Kiayias, Nikos Leonardos, and Giorgos Panagiotakos


The Bitcoin backbone protocol [Eurocrypt 2015] extracts basic properties of Bitcoin's underlying {\em blockchain} data structure, such as ``common prefix'' and ``chain quality,'' and shows how fundamental applications including consensus and a robust public transaction ledger can be built on top of them. The underlying assumptions are ``proofs of work'' (POWs), adversarial hashing power strictly less than $1/2$ {\em and} no adversarial pre-computation---or, alternatively, the existence of an unpredictable ``genesis'' block. In this paper we first show how to remove the latter assumption, presenting a ``bootstrapped'' Bitcoin-like blockchain protocol relying on POWs that builds genesis blocks ``from scratch'' in the presence of adversarial pre-computation. Importantly, the round complexity of the genesis block generation process is \emph{independent} of the number of participants. Next, we consider applications of our construction, including a PKI generation protocol and a consensus protocol without trusted setup assuming an honest majority (in terms of computational power). Previous results in the same setting (unauthenticated parties, no trusted setup, POWs) required a round complexity linear in the number of participants.

Available format(s)
Cryptographic protocols
Publication info
A minor revision of an IACR publication in PKC 2018
Contact author(s)
pagio91i @ gmail com
2018-03-23: last of 3 revisions
2016-10-17: received
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Creative Commons Attribution


      author = {Juan A.  Garay and Aggelos Kiayias and Nikos Leonardos and Giorgos Panagiotakos},
      title = {Bootstrapping the Blockchain, with Applications to Consensus and Fast PKI Setup},
      howpublished = {Cryptology ePrint Archive, Paper 2016/991},
      year = {2016},
      note = {\url{}},
      url = {}
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