Zcash will activate its NU6.3 "Ironwood" network upgrade at block 3,428,143, expected around July 28. This update replaces the existing Orchard shielded transaction pool with a newly tracked system aimed at improving supply verification after a security flaw was discovered.

Shielded Pool Overhaul and Supply Protection

The Ironwood upgrade introduces a separate note commitment tree and nullifier set, enabling nodes to independently track the new shielded pool distinct from Orchard. This change is critical because a bug found in the Orchard pool allowed the theoretical creation of counterfeit ZEC without a clear public record. Although no exploitation has been detected, Zcash developers patched the issue with emergency releases in June and cannot conclusively rule out hidden inflation due to privacy protections.

One of Ironwood's key features is a "turnstile" mechanism that restricts the amount of ZEC leaving Orchard to the amount that legitimately entered it. After activation, Orchard will become exit-only, preventing further deposits while allowing withdrawals capped by prior inflow. This design lets the community publicly verify circulating supply without exposing sensitive transaction details, trapping any excess value within Orchard if irregularities exist.

Additional Enhancements and Upgrade Requirements

The upgrade also introduces a new version 6 transaction format and supports quantum-recoverable notes, though it does not make Zcash quantum-secure immediately. The Zcash Foundation’s Zebra 6.0.0 node software release highlights that operators must update before the fork because older versions will fail to follow the correct chain after activation.

The estimated activation time is around 13:00 UTC on July 28. Node commands have been updated to allow operators to inspect shielded pool values and their commitment trees. This upgrade follows the pattern of cautious but necessary improvements following the earlier patch, emphasizing sound money principles and transparency in supply.

This material is for informational purposes only and does not constitute financial advice.