Here’s another refined rewrite with a slightly sharper, more concise tone:
Zcash developers have locked in the consensus changes for the Ironwood upgrade, with activation targeted for late July at block height 3,417,100. The update addresses a critical flaw in the Orchard shielded pool that could have enabled the undetectable minting of unlimited counterfeit ZEC.
Ironwood introduces a new shielded pool, strengthens supply enforcement through the existing turnstile mechanism, and blocks any new deposits into the compromised Orchard pool. The upgrade is supported by formally verified zero-knowledge circuits and independent third-party security audits.
The Orchard Flaw and Its Implications
Launched in May 2022 as part of the NU5 upgrade, the Orchard pool incorporated the Halo 2 proving system and marked a major step forward in Zcash’s privacy architecture. It allows fully shielded transactions by hiding amounts and participant identities without requiring a trusted setup.
In early 2026, researchers uncovered a vulnerability in the circuit design that could have allowed attackers to create counterfeit ZEC with no visible on-chain trace.
This flaw effectively broke supply guarantees within the Orchard pool. The same privacy features that shield legitimate transactions also made any unauthorized issuance invisible—even to the Zcash team itself.
The issue was identified through an AI-assisted external audit, leading to a discreet patch and coordinated disclosure before Ironwood was formally introduced.
Turnstile Enforcement and the New Pool Design
Ironwood is being developed through a joint effort involving ZODL, Tachyon, Valar Group, the Zcash Foundation, and Shielded Labs, reflecting a multi-party governance model.
At the center of the upgrade is a redesigned Orchard circuit that introduces a control flag capable of restricting payments within a pool while still allowing change outputs, preserving privacy functionality.
Once activated, this restriction will be permanently applied to the legacy Orchard pool. All new Orchard transactions will be routed automatically to the replacement pool, while tighter constraints on the valueBalance field enforce supply limits.
The upgrade relies on the existing turnstile mechanism to maintain supply integrity. Any ZEC leaving the old Orchard pool must pass through the turnstile before entering the new one, ensuring that the amount transferred cannot exceed the amount originally deposited.
This structure restores enforceable supply bounds. After migration, full nodes will be able to independently verify that no counterfeit ZEC has entered the new pool, re-establishing trustless supply validation at the protocol level.
The activation is aligned with the end-of-support for zcashd at block height 3,417,100. Ahead of mainnet deployment, the upgrade will undergo testnet validation, ecosystem coordination, and final audits. Wallet providers are expected to roll out one-click migration tools, while the new pool maintains compatibility with existing Orchard addresses, avoiding the need for key rotation.
