Source: Zodl Support. Distilled and processed for Signal; not original content.
TL;DR
Zcash is rotating its default shielded pool from Orchard to Ironwood (activation targeted July 28, 2026) after a soundness issue in Orchard was responsibly disclosed and remediated in the NU6.2 upgrade. The migration is a masterclass in two durable patterns: how a chain proves supply integrity across a pool rotation (the turnstile), and how a wallet moves user funds between privacy domains without deanonymizing them (split transfers, randomized timing, Tor routing).
Actionable items
- Cross-pool transfers reveal amounts on-chain even when addresses stay hidden. Any migration between privacy domains is a correlation surface: treat the amount plus timing as the leak, not just the addresses.
- To migrate privately, split the balance into several smaller transfers, spread them over time, and vary the timing. One big transfer at activation is trivially linkable.
- Route migration traffic through Tor (or a trusted VPN) or the remote server can link your IP to the migration amounts. Network-level privacy and on-chain privacy fail independently: you need both.
- Broadcast transactions over a different server than the one used for syncing, so the sync provider cannot pair your reads with your writes.
- Supply integrity across a pool rotation can be guaranteed trustlessly with a turnstile: the protocol refuses to let more value exit the old pool than entered it, so users get assurance independent of when (or whether) any individual migrates.
- Incident-response pattern worth copying: responsible disclosure, coordinated network upgrade to remediate (NU6.2), then rotate to a hardened replacement backed by formal verification and independent audits, with no forced deadline for users.
- Wallet UX lesson: background transfer schedules are best-effort on mobile (battery modes, Background App Refresh). Design the flow so reopening the app always shows progress and prompts the next pending step, instead of relying on notifications.
- Keep receiving addresses stable across the rotation. Ironwood reuses existing Orchard receivers, so previously shared addresses keep working: rotation is invisible to counterparties.
Key quotes
Because the turnstile won’t allow more ZEC to move out than went in, everyone receives a trustless guarantee that the circulating supply does not exceed the amount in Orchard, independent of when any individual migrates.
Moving funds between pools reveals the amount of the transactions on the public Zcash blockchain (but not the originating or destination addresses), so spreading the transfers out and varying their timing make it much harder for an outside observer to link them to your wallet.