Paper 2022/1205

Accountable Light Client Systems for PoS Blockchains

Oana Ciobotaru, Web3 Foundation
Fatemeh Shirazi, Independent Researcher
Alistair Stewart, Web3 Foundation
Sergey Vasilyev, Web3 Foundation

A major challenge for blockchain interoperability is having an on-chain light client protocol that is both efficient and secure. We present a protocol that provides short proofs about the state of a decentralised consensus protocol while being able to detect misbehaving parties. To do this naively, a verifier would need to maintain an updated list of all participants' public keys which makes the corresponding proofs long. In general, existing solutions either lack accountability or are not efficient. We define and design a committee key scheme with short proofs that do not include any of the individual participants' public keys in plain. Our committee key scheme, in turn, uses a custom designed SNARK which has a fast prover time. Moreover, using our committee key scheme, we define and design an accountable light client system as the main cryptographic core for building bridges between proof of stake blockchains. Finally, we implement a prototype of our custom SNARK for which we provide benchmarks.

Note: Revised version. Includes updated related work and an informal overview of the light client system model.

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Publication info
accountable light client systemscommittee key schemescommit-and-provecustom SNARKs
Contact author(s)
oana @ web3 foundation
alistair @ web3 foundation
2023-01-12: last of 3 revisions
2022-09-12: received
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      author = {Oana Ciobotaru and Fatemeh Shirazi and Alistair Stewart and Sergey Vasilyev},
      title = {Accountable Light Client Systems for PoS Blockchains},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1205},
      year = {2022},
      note = {\url{}},
      url = {}
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