Paper 2020/643

About Blockchain Interoperability

Pascal Lafourcade and Marius Lombard-Platet


A blockchain is designed to be a self-sufficient decentralised ledger: a peer verifying the validity of past transactions only needs to download the blockchain (the ledger) and nothing else. However, it might be of interest to make two different blockchains interoperable, i.e., to allow one to transmit information from one blockchain to another blockchain. In this paper, we give a formalisation of this problem, and we prove that blockchain interoperability is impossible according to the classical definition of a blockchain. Under a weaker definition of blockchain, we demonstrate that two blockchains are interoperable is equivalent to creating a `2-in-1' blockchain containing both ledgers, thus limiting the theoretical interest of making interoperable blockchains in the first place. We also observe that all practical existing interoperable blockchain frameworks work indeed by exchanging already created tokens between two blockchains and not by offering the possibility to transfer tokens from one blockchain to another one, which implies a modification of the balance of total created tokens on both blockchains. It confirms that having interoperability is only possible by creating a `2-in-1' blockchain containing both ledgers.

Note: First version of this paper was sent to IPL the 13/08/2019

Available format(s)
Publication info
Published elsewhere. Information Processing Letters
decentralised ledgerinteroperabilityblockchain
Contact author(s)
marius lombard-platet @ ens fr
pascal lafourcade @ uca fr
2020-06-03: received
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Creative Commons Attribution


      author = {Pascal Lafourcade and Marius Lombard-Platet},
      title = {About Blockchain Interoperability},
      howpublished = {Cryptology ePrint Archive, Paper 2020/643},
      year = {2020},
      doi = {10.1016/j.ipl.2020.105976},
      note = {\url{}},
      url = {}
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