Zcash’s Ironwood Upgrade to Lock Orchard Pool at Block 3,428,143

What Changes After Activation

The main practical change for users is that Orchard will become a one-way pool. Existing balances stay in place, and the same address format will continue to work because the new pool reuses the old address. However, wallets are still building migration tools, so some balances may temporarily appear difficult to move until wallet providers complete their updates.

For infrastructure providers, the deadline is more immediate. Node operators are expected to install the Zcash Foundation’s Zebra 6.0.0 release before Tuesday, as that software defines the switch-over point for the upgrade. Some exchanges may also temporarily pause deposits or withdrawals during the transition. Developers have said such interruptions would reflect exchange readiness rather than a problem with the network itself.

Ironwood also introduces a safeguard tied to ZIP 2005. Developers describe it as a quantum-related protection mechanism that would allow funds in the new pool to be rescued if future quantum computers were ever able to break current cryptographic assumptions. The source material notes that this is not full quantum protection.

Privacy Risk During Migration

Although moving coins out of Orchard does not publicly reveal sender or recipient identities, the withdrawal amount is visible on-chain. Developers and project figures have warned that this can still create a privacy risk if wallet traffic is linked to a user’s IP address by the server the wallet communicates with.

Zcash founder Zooko Wilcox said in user guidance that network-level privacy should come first when users eventually migrate funds. His recommendation was to enable Tor or Nym before moving coins and to wait until wallet providers confirm that migration is safe.

Why Zcash Is Freezing New Orchard Deposits

The Ironwood change follows the discovery of a bug in May by Shielded Labs researcher Taylor Hornby. According to the project, the flaw affected the mathematical proof system used to validate Orchard payments and could have allowed counterfeit ZEC to be created without detection.

ZODL, the Zcash Open Development Lab, said it patched the issue within days. But because Orchard hides transaction amounts, the network could not prove that no invalid coins had ever been minted. Ironwood’s answer is to isolate the old pool with what developers describe as a turnstile mechanism: funds can leave, but the system will not allow more ZEC to exit than originally entered. If counterfeit coins were ever created, the design is meant to trap them inside the locked pool permanently.

The source article says the fix is backed by outside auditors and formal verification. A joint statement attributed to Sean Bowe and Dev Ojha said the change goes beyond simply encouraging users to migrate by effectively forcing wallets to use the new pool for Orchard transactions.

A Repeat of a 2018 Problem

The current situation echoes an earlier episode in Zcash’s history. In March 2018, cryptographer Ariel Gabizon found a counterfeit-coin bug in Sprout, the project’s first private pool. The fix was later included in the Sapling upgrade, while full disclosure came months afterward in February 2019.

That earlier repair prevented new fake coins from being created but could not prove whether any had already been minted. Sprout was eventually closed to new use and left behind. The source article notes that 22,747 ZEC remain in that pool and says no one has ever broken its turnstile, which is treated as the best available evidence that no counterfeit coins were extracted.

Over the next month, the migration out of Orchard will be visible through a ZODL dashboard that tracks funds leaving the pool block by block. The speed of that process may matter: a slow migration would leave a large amount of private ZEC temporarily unusable, while a fast migration could strengthen supply verification but reduce privacy.