DarkDrop is a zero-knowledge privacy protocol on Solana for unlinkable peer-to-peer SOL transfers. Built around a custom credit note architecture where the deposit and withdrawal transactions remain cryptographically unlinked at the proof level. Users deposit SOL, receive a claim code, and share it with a recipient through any off-chain channel. The recipient generates a ZK proof in-browser and pulls the funds to any wallet. The protocol implements three privacy paths: direct (with revoke option), private (gasless via relayer), and maximum privacy (recursive two-layer ZK via the note pool).