Decoupling consensus from transaction verification and execution is an
important technique to increase the throughput of blockchains, a technique
known as a lazy blockchain. Lazy blockchains can end up containing invalid
transactions such as double spends, but these can easily be filtered out by
full nodes that can check if there have been previous conflicting transactions.
However, creating light (SPV) clients that do not see the whole transaction
history on top of these chains becomes a challenge: A record of a transaction
on the chain does not necessarily entail transaction confirmation. In this
paper, we devise a protocol that enables the creation of efficient light
clients for lazy blockchains. The number of interaction rounds and the
communication complexity of our protocol are only logarithmic in the blockchain
execution time. Our construction is based on a bisection game that traverses
the Merkle tree containing the ledger of all — valid or invalid —
transactions. We prove that our proof system is succinct, complete and sound,
and we illustrate how it can be applied to both the UTXO as well as the account
based models. Lastly, we empirically demonstrate the feasibility of our scheme
by providing experimental results.
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Author Of this post: <a href="http://arxiv.org/find/cs/1/au:+Tas_E/0/1/0/all/0/1">Ertem Nusret Tas</a>, <a href="http://arxiv.org/find/cs/1/au:+Zindros_D/0/1/0/all/0/1">Dionysis Zindros</a>, <a href="http://arxiv.org/find/cs/1/au:+Yang_L/0/1/0/all/0/1">Lei Yang</a>, <a href="http://arxiv.org/find/cs/1/au:+Tse_D/0/1/0/all/0/1">David Tse</a>