SNACKs: Leveraging Proofs of Sequential Work for Blockchain Light Clients
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Date
2022
Publication Type
Conference Paper
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yes
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Abstract
The success of blockchains has led to ever-growing ledgers that are stored by all participating full nodes. In contrast, light clients only store small amounts of blockchain-related data and rely on the mediation of full nodes when interacting with the ledger. A broader adoption of blockchains calls for protocols that make this interaction trustless. We revisit the design of light-client blockchain protocols from the perspective of classical proof-system theory, and explain the role that proofs of sequential work (PoSWs) can play in it. To this end, we define a new primitive called succinct non-interactive argument of chain knowledge (SNACK), a non-interactive proof system that provides clear security guarantees to a verifier (a light client) even when interacting only with a single dishonest prover (a full node). We show how augmenting any blockchain with any graph-labeling PoSW (GL-PoSW) enables SNACK proofs for this blockchain. We also provide a unified and extended definition of GL-PoSWs covering all existing constructions, and describe two new variants. We then show how SNACKs can be used to construct light-client protocols, and highlight some deficiencies of existing designs, along with mitigations. Finally, we introduce incremental SNACKs which could potentially provide a new approach to light mining.
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Publication status
published
External links
Book title
Advances in Cryptology – ASIACRYPT 2022
Journal / series
Volume
13791
Pages / Article No.
806 - 836
Publisher
Springer
Event
28th International Conference on the Theory and Application of Cryptology and Information Security (Asiacrypt 2022)
Edition / version
Methods
Software
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Date collected
Date created
Subject
Blockchains; Light clients; Proofs of sequential work
Organisational unit
09693 - Hofheinz, Dennis / Hofheinz, Dennis
Notes
Conference lecture held on December 6, 2022.