Zcash launches its Ironwood upgrade on Tuesday at block 3,428,143, permanently locking the Orchard private pool containing 3.76 million ZEC worth $1.89 billion. The upgrade responds to a counterfeiting vulnerability discovered by researcher Taylor Hornby in May, which could have enabled creation of fake ZEC without detection. The locked pool represents 22% of all ZEC in circulation, and while existing balances remain secure, holders can only withdraw funds from the pool and cannot make new deposits.
Ironwood Upgrade Changes User Access to Orchard Pool
Balances inside the locked pool remain safe, and existing addresses continue to function because the new pool reuses them. Developers state most holders do not need to take immediate action.
Wallets are still building migration tools. Until a wallet completes this development, balances may appear stuck to users.
Node operators must install the Zcash Foundation's Zebra 6.0.0 release before Tuesday. This release sets the activation point for the upgrade.
Some exchanges may pause deposits or withdrawals during the transition. Developers clarify that such pauses indicate the exchange is updating systems, not that Zcash itself has malfunctioned.
The new pool incorporates a quantum safeguard from ZIP 2005. If quantum computers break current cryptographic methods, funds in the new pool could be recovered, while coins in old pools could not. This does not constitute full quantum protection.
Migration Process Exposes Transaction Amounts and IP Addresses
Moving funds out of the old pool makes transaction amounts publicly visible. The sender and receiver identities remain hidden.
Wallets connect to servers that can see user IP addresses. Observers can potentially link visible transaction amounts to specific IP addresses, compromising user privacy.
Zooko Wilcox, who founded Zcash, wrote in project user guidance: "So for every user, the number one most important issue is having network-level privacy (i.e. Tor or Nym) before migrating."
Wilcox advises users to activate Tor or Nym before migrating, then wait for wallet developers to confirm migration safety. He also warned that scammers are impersonating Ironwood migration support.
Counterfeiting Vulnerability Prompted Emergency Pool Lock
Taylor Hornby, working for Shielded Labs, discovered a flaw in May in the mathematical proofs validating Orchard payments. The vulnerability could have allowed creation of counterfeit ZEC without detection.
ZODL, the Zcash Open Development Lab, patched the bug within days. ZEC dropped more than 30% following the public disclosure, falling as low as $385.80.
Orchard's design hides all transaction amounts, making it impossible to verify whether counterfeit coins were ever created. Ironwood addresses this through a turnstile mechanism that functions as a counter, preventing more ZEC from exiting the pool than entered it. Any counterfeit coins, if they exist, remain trapped inside permanently.
Sean Bowe and Dev Ojha wrote in a joint statement from Project Tachyon and Valar Group: "However, rather than merely asking users to migrate away from a deprecated pool, we are effectively forcing wallets to conduct Orchard transactions in the new pool."
Outside auditors and formal verification work support the fix.
Zcash Closed Sprout Pool After Similar Bug in 2018
Cryptographer Ariel Gabizon found a counterfeiting vulnerability in Sprout, Zcash's first private pool, in March 2018. The company kept the discovery confidential for 11 months, incorporating the fix into the Sapling upgrade in October 2018. The full disclosure occurred in February 2019.
That fix prevented new counterfeit coins but could not verify whether fake coins were created before the patch. The Sprout pool was closed and abandoned. Eight years later, 22,747 ZEC remain in that pool, and the turnstile has never been breached.
| Comparison | Sprout, 2018 | Orchard, 2026 |
|:-----------|:-------------|:--------------|
| Bug found | March 2018 | May 2026 |
| Made public | 11 months later | Within days |
| How it was fixed | Quietly, inside Sapling | Patch, then Ironwood |
| Old pool | Left open, moving optional | Locked, moving required |
| ZEC involved | 22,747 still stuck | 3,765,594 to move |
Ironwood differs by requiring migration rather than making it optional.
ZODL Dashboard Tracks Real-Time Migration Progress
ZODL's dashboard displays funds leaving Orchard block by block. Slow migration leaves a significant portion of private ZEC unusable. Rapid migration strengthens the supply verification but reduces privacy through concentrated activity.
ZEC traded near $506 on Monday, up 4% in a day and 22% in a month. Over the past year it gained more than 1,100%, a performance that placed it in Forbes' 2026 top 10.
FAQ
What happens to ZEC in the old Orchard pool after Tuesday?
Balances remain secure inside the locked pool at block 3,428,143. Users can withdraw funds but cannot deposit new ZEC into the old pool. Existing addresses continue working because the new pool reuses them.
Why does migrating funds expose transaction amounts?
Moving ZEC out of the old pool makes the transaction amount publicly visible, though sender and receiver identities stay hidden. Wallets connect to servers that see IP addresses, allowing observers to potentially link visible amounts to specific users without Tor or Nym protection.
How does Ironwood differ from the 2018 Sprout fix?
The 2018 Sprout fix was implemented quietly within the Sapling upgrade and left the old pool open with optional migration. Ironwood locks the Orchard pool immediately at activation and requires migration, with the turnstile mechanism preventing more ZEC from exiting than entered.
