Zcash activates Ironwood upgrade and replaces Orchard

Zcash has activated its Ironwood network upgrade, creating a new shielded pool intended to take over private transactions after a flaw in the previous Orchard pool raised the theoretical risk of undetectable counterfeit ZEC. The upgrade went live at block height 3,428,143 under the NU6.3 network change, placing Orchard into a withdrawal-only mode and directing new shielded activity toward Ironwood.

The transition creates a controlled exit route from Orchard while preventing funds in the older pool from returning to the broader Zcash supply. Users can choose whether and when to withdraw their Orchard funds, but cannot send new shielded funds into the pool. That structure gives the network a way to retire Orchard without forcing an immediate, chain-wide migration of private balances.

Ironwood uses the corrected version of Orchard’s zero-knowledge circuit and retains its Halo 2 proving system, with modifications designed for the replacement pool. The new shielded pool has also undergone formal verification, a mathematical testing process intended to show that software follows its specified rules across a wide range of possible conditions.

Orchard balances remain the main migration challenge

Orchard had become Zcash’s dominant privacy pool before its restriction, holding nearly 88% of the network’s shielded ZEC supply at its peak. Sapling and the much older Sprout pool accounted for the remaining shielded balances.

A migration tracker reported that 40,207 ZEC had moved into Ironwood following activation, while roughly 3.6 million ZEC remained in Orchard. The size of that balance means the upgrade will remain relevant well beyond its activation block: the network’s shielded supply will need to pass through the Orchard exit mechanism before users can access Ironwood’s privacy features.

The withdrawal-only design also creates a practical distinction for wallet providers, payment services and node operators. Software handling shielded ZEC must support Ironwood’s rules before it can receive or send funds through the new pool. Users keeping ZEC with third-party custodians could encounter temporary service interruptions as those providers complete their own upgrades.

Individuals operating Zcash nodes need to run software compatible with NU6.3 to remain synchronized with the network. Wallet users should check whether their application supports Ironwood before attempting a shielded transfer, particularly when moving balances from Orchard.

Counterfeiting concern prompted emergency response

The upgrade follows the discovery in late May of a vulnerability in Orchard’s zero-knowledge circuit. Taylor Hornby, a researcher at Shielded Labs, identified a flaw that could theoretically have allowed counterfeit ZEC to be created inside Orchard without public detection.

Zcash’s privacy architecture hides the amounts and addresses involved in shielded transfers. That protection is central to the network’s purpose, but it also makes supply integrity especially sensitive: a counterfeit coin created within a private pool could be difficult to identify through ordinary blockchain monitoring.

The Zcash network responded with an emergency soft fork on June 2 that disabled Orchard activity. A hard fork the following day applied corrected circuit code. Ironwood extends that response by establishing a separate pool built around the patched code rather than reopening Orchard for normal use.

The migration arrangement is designed to contain any hypothetical problem inside the older pool. Once ZEC leaves Orchard, the network’s new boundary rules prevent it from moving back in, limiting the amount that can emerge from the legacy shielded environment.

Turnstile gives supply auditors a clearer boundary

Ironwood adds a “turnstile” mechanism that caps the amount of ZEC that can leave Orchard and makes the transition independently auditable. The control is meant to help verify that the Orchard flaw did not lead to an increase in Zcash’s circulating supply beyond its 21 million ZEC cap.

That feature addresses the central difficulty posed by the vulnerability. Zcash cannot simply rely on visible transaction history to assess every movement inside a shielded pool, because its private transfer design intentionally conceals those details. The turnstile instead creates an observable limit at the point where value exits Orchard.

The upgrade also introduces quantum-recoverable notes under ZIP 2005. These notes are designed to provide a recovery path if future advances in quantum computing weaken cryptographic assumptions used by existing shielded funds. The feature does not imply that present-day quantum systems can break Zcash’s privacy technology, but it adds an option for handling a long-term cryptographic risk that privacy networks must consider.

ZODL and external teams contributed to the transition

The repair and migration involved the Zcash Open Development Lab, Project Tachyon, Valar Group, the Zcash Foundation and Shielded Labs. Josh Swihart, executive director of the Zcash Open Development Lab, said 14 ZODL engineers produced 82% of merged changes across Zcash protocol and wallet repositories connected to the fix and Ironwood transition.

The breadth of the work reflects the operational scope of replacing a shielded pool. Core protocol changes alone would not complete the migration; wallets, node software and related infrastructure also need to recognize the new pool and guide users through the transition.

ZEC price remains volatile after disclosure

ZEC fell about 9% on Tuesday to roughly $460 before recovering toward $475. The token had already dropped more than 50% following disclosure of the Orchard vulnerability, after previously rising from about $45 in September last year to around $700 by year-end.

The price reaction has left traders focused on whether the Ironwood migration proceeds smoothly and whether supply auditing can resolve concerns around the earlier flaw. The newly activated controls do not require Orchard holders to move immediately, but they make the pace of those withdrawals a visible measure of how quickly Zcash’s private liquidity shifts into the replacement system.