FlyClient Guide
Succinct chain verification: the sampling protocol, the deployed ZIP-221 commitment, and the unbuilt bridge

Abstract

Assuming the commitment foundations of the Crypto Guide, the deployed chain-selection rules of the Consensus Guide, the block structures of the Ironwood Guide, and the light-client layer of the Wallet Guide, this volume of The Zcash Arboretum documents succinct chain verification for Zcash: the FlyClient protocol as its paper constructs it, the ZIP-221 chain-history commitment that every post-activation Zcash block header has carried since Heartwood, and the distance between the two. The commitment is consensus-critical and required in valid post-activation headers; none of the light-client implementations examined here consumes it. Claims about the deployed tree cite the ZIPs and the implementations; claims about the sampling protocol carry the paper’s own model assumptions, and its printed defects are registered rather than silently repaired; the bridge between the two is classified plainly as unbuilt.