Zcash greenlights Ironwood to fix Orchard flaw, targets July

Zcash developers finalized a package of consensus-rule changes called Ironwood to address a flaw in the Orchard shielded pool that could have allowed attackers to mint unlimited counterfeit ZEC. The proposal creates a new Orchard-based shielded pool and imposes limits on the existing pool. The team is targeting late July for activation but warned the date could change.

Under Ironwood, the Orchard circuit used by both pools will include a flag. When enabled for the old pool, the flag will disable payments to other users inside that pool while still allowing wallets to create change notes. Zcash developer Sean Bowe wrote on X that this “enables a privacy safeguard.” Wallet software will also constrain a field called valueBalance to block new incoming payments to the old pool. New payments sent to Orchard receivers will be routed to the new Ironwood pool.

The upgrade relies on the existing turnstile mechanism to keep the reported circulating supply of ZEC bounded. Bowe wrote: “This combination enforces a bound on the circulating supply of ZEC through the use of the existing turnstile mechanism; the amount of ZEC that anyone can transact with is no more than the amount that is supposed to exist.” The plan allows users to migrate funds from the old pool into the new pool to reduce exposure and to provide evidence about whether counterfeit minting occurred.

Developers will move into implementation, finalize specifications, and coordinate support across wallets and services. The team plans audits and formal verification of the new circuit. The Zcash Open Development Lab is targeting late July for activation; Zcash co-founder Zooko Wilcox cautioned the timeline remains uncertain.

Markets reacted sharply after the vulnerability was disclosed. ZEC fell from roughly $630 to about $303, a drop of more than 50%, and later recovered to near $450. Some traders exited positions; BitMEX co-founder Arthur Hayes liquidated his entire ZEC holding following the disclosure. Zcash developers and community leaders used the incident to test incident response and improve coordination. Josh Swihart, founder of the Zcash Open Development Lab, wrote: “We resolved the issue, battle-tested our incident support processes, built stronger relationships with others who support the network, tested our own resilience, and unified as a community of builders to agree on a path forward.”

Orchard is Zcash's primary shielded transaction pool and uses zero-knowledge proofs to verify transactions without revealing details. Ironwood's changes aim to address the supply-integrity vulnerability while preserving private transaction flows. The upgrade will require timely updates from wallets and other ecosystem software so users can migrate funds and use the new Orchard pool once Ironwood activates.