Zcash has activated the Ironwood upgrade, effectively sealing a $1.7 billion shielded pool and retiring the older Orchard pool where a counterfeiting bug went undetected for four years. The upgrade introduces a new withdrawal gate that caps exits at verified deposits.
Why the upgrade was needed
The Orchard pool, launched in 2020, was designed to offer private transactions. But a bug in its code allowed an attacker to create coins out of thin air. For four years, that vulnerability remained hidden. No one knows if it was ever exploited. The risk was real: any counterfeit coins could have been spent without detection, undermining the entire supply.
Zcash developers decided the only safe fix was to retire the pool entirely. The Ironwood upgrade does that. It forces all coins still in the shielded pool to move through a new gate. That gate checks each withdrawal against the user's verified deposit history. If someone tries to pull out more than they put in, the transaction is blocked.
How the new gate works
The gate is a smart contract-like mechanism built into the upgrade. Every coin leaving the shielded pool must pass through it. The gate compares the withdrawal amount to the user's cumulative deposits. If the numbers match, the transaction goes through. If not, it's rejected. This prevents any counterfeit coins from escaping into the transparent pool or being spent elsewhere.
Importantly, the gate doesn't require users to reveal their transaction details. It works with zero-knowledge proofs, preserving privacy while enforcing the deposit cap. The $1.7 billion pool is now sealed. Coins that were already in the pool before the upgrade remain there, but they can only exit under the new rules.
For anyone holding Zcash in the shielded pool, the upgrade is automatic. No action is needed. But the old Orchard pool is no longer usable. Any funds still in it are effectively frozen unless they are moved through the gate. Users who had legitimate deposits can still withdraw their coins. The gate ensures they get back exactly what they put in.
The upgrade also means the counterfeiting bug is no longer a threat. Even if an attacker knew about it, they can't exploit it now. The pool is retired, the gate is in place. The Zcash network has moved on.
Timeline and next steps
The Ironwood upgrade was activated on the Zcash mainnet. The exact block height was predetermined by the development team. The upgrade was adopted by miners and nodes across the network. There were no reported issues during the activation.
With the upgrade live, the Zcash development team is now focused on future improvements. The old Orchard pool is officially retired. The shielded pool remains, but under the new rules. The $1.7 billion in value is now protected by the gate.
