TL;DR
- Zcash activated its Ironwood upgrade July 28 and closed the Orchard shielded pool to new value.
- Orchard’s roughly 3.66 million ZEC was not stolen or confirmed as counterfeit and can still leave through a supply-accounting checkpoint.
- Migration is voluntary, while wallet readiness, its completion date and any historical exploitation remain unresolved.
Zcash activated its Ironwood network upgrade on July 28, closing the older Orchard shielded pool, a part of the network that stores private transactions, to new funds. The network simultaneously opened a separately tracked private pool for future shielded transactions.
Orchard contained a critical flaw that could have allowed someone to create counterfeit ZEC without leaving an obvious public record. Developers fixed the immediate vulnerability in early June. However, that repair could not prove whether anyone had exploited the flaw during the previous four years.
Ironwood creates a clean starting point for shielded funds. Orchard users can still withdraw or migrate their ZEC, but the transfer will happen gradually through compatible wallets.
The vulnerability behind the upgrade
Zcash uses shielded pools to keep transaction details private while still checking that transactions follow network rules. The Orchard flaw affected the circuit responsible for that control process.
Researcher Taylor Hornby discovered the vulnerability on May 29 using Anthropic’s Claude Opus 4.8 as part of an AI-assisted security audit commissioned by Shielded Labs, shortly after the model’s public release. According to a Shielded Labs disclosure, developers deployed an emergency fix within days of the disclosure. Public analysis has not established that anyone created counterfeit ZEC.
A public checkpoint protects the migration
Still, Zcash’s private design means the blockchain cannot provide a complete historical answer. Therefore, the migration uses an accounting boundary described as a turnstile.
The network publicly recorded how much legitimate value entered Orchard. Its rules now prevent more value from leaving than that recorded amount. Any counterfeit ZEC that might exist beyond the verified balance could not cross the boundary.
This supply check is the main security purpose behind Zcash’s upgrade to Ironwood. It does not expose individual transactions or remove the privacy features of the new pool.
Orchard can release funds but cannot receive more
Zcash activated Ironwood at mainnet block 3,428,143. From that block onward, network rules prevent new value from entering Orchard. They also stop ordinary transfers between users from remaining inside the older pool.
Value already held in Orchard is fully available to owners. They can move it into Ironwood or withdraw it to another supported Zcash address. The new pool started with a separate transaction history and a zero balance.
CoinDesk reported that Orchard held about 3.66 million ZEC when Ironwood activated. That amount was worth roughly $1.7 billion at the reported market price. Around 1,500 ZEC had already moved into Ironwood by the publication cutoff. That leaves the bulk of Orchard’s 3.66 million ZEC still waiting to migrate.
Wallet support will shape the migration
Moving Orchard funds is voluntary and user-driven. In fact, not every ZEC holder needs to act immediately, since a lot of coins sit outside Orchard entirely.
However, Orchard users need wallet software that supports Ironwood and handles the migration safely. Wallet readiness matters because a poorly designed transfer can reveal more transaction information than the user intended.
The Zcash community has published several dashboards tracking how much value crosses into Ironwood. These tools can measure total movement between pools without identifying the people involved.
The final migration timeline remains unknown. Some funds may stay in Orchard for an extended period because their owners are inactive, waiting for wallet updates or choosing not to move.
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Ironwood adds a future recovery feature
Ironwood also changes how the network records shielded notes. The new format is designed to support recovery if future quantum computers break the cryptography that protects today’s private balances.
This feature does not quantum-proof Zcash now, but it preserves information that could support a later recovery process after the network adopts new cryptography.
The new pool also has its own balance records, note tree and list of previously spent notes. So nodes can track Ironwood independently from Orchard while maintaining private transaction details.
Formal verification of the new circuit is still in progress, and wallet and exchange support will differ by provider. Migration speed now depends less on Zcash’s code than on how quickly individual wallets adopt it.
