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Zcash’s Ironwood network upgrade is scheduled to activate on July 28, giving the privacy-focused blockchain a new shielded pool after developers and security researchers disclosed a serious flaw in its Orchard pool.
The upgrade is set for block height 3,428,143, with activation expected around 8 a.m. Eastern time.
Upgrade Moves One Week Later Than Planned
Core developer Sean Bowe said the Ironwood mainnet activation height has been set and tagged.
The date is one week later than an earlier July 21 target. Some ecosystem participants had warned that exchanges, mining pools and wallet teams needed more time to prepare for the network change.
The upgrade is known as NU6.3. It follows a fast review process after the Orchard soundness issue was disclosed in June.
Orchard Pool Will Close to New Activity
Ironwood is designed to replace the existing Orchard shielded pool. After activation, the current Orchard pool will close to new deposits and internal transactions.
Funds will still be able to move out, but they must pass through an accounting checkpoint before entering the new Ironwood pool.
The checkpoint is intended to verify that no more ZEC leaves Orchard than properly entered it, giving the network a way to check supply integrity without exposing private transaction details.
Bug Raised Counterfeit ZEC Risk
Developers said the Orchard issue could have allowed an attacker to create counterfeit ZEC inside the shielded pool. The bug was present from Orchard’s activation in May 2022 until an emergency fix was deployed on June 1.
Developers said there was no evidence that the flaw was exploited, no evidence of user-fund impact and no evidence of a change to total ZEC supply.
Because Orchard is private by design, chain data alone cannot prove whether the flaw was exploited before the fix. The checkpoint is intended to detect any imbalance if invalid funds are moved out of Orchard.
Wallets and Exchanges Must Prepare by July 28
The upgrade puts pressure on Zcash infrastructure providers to be ready before the activation height. Wallets that support Orchard are expected to help users migrate funds into Ironwood after activation.
The plan keeps existing Orchard receivers usable, so users should not need new addresses for ordinary receiving flows. Node operators, exchanges, mining pools and wallet providers need compatible software before July 28 to avoid disruption around shielded fund access.
