Zcash activated its Ironwood network upgrade on Tuesday, replacing the vulnerable Orchard shielded pool with a new, independently verifiable system. The upgrade, which went live at block height 3,428,143, is designed to restore the ability for users and third parties to audit the cryptocurrency's circulating supply without relying on a trusted setup. The migration involves roughly $1.8 billion in value.
Inside the Ironwood upgrade
The upgrade, formally designated NU6.3, introduces a separate Ironwood shielded pool, a new transaction format, and a mandatory accounting checkpoint. The checkpoint forces all shielded transactions to go through a verifiable accounting step, closing the loophole that made the Orchard pool vulnerable. The new transaction format is backward-incompatible, meaning old software won't work with the new pool — users had to update their wallets before the activation.
The $1.8 billion migration
Moving that much value from one shielded pool to another is no small task. The Ironwood upgrade doesn't automatically transfer funds; users must manually move their Zcash from the old Orchard pool to the new Ironwood pool. The Zcash Foundation has published migration guides, but the process could take days or weeks depending on user adoption. The old Orchard pool remains functional for now, but the team has said it will eventually be deprecated.
Why the upgrade was needed
The Orchard shielded pool, launched in 2022, had a vulnerability that allowed a sophisticated attacker to inflate the supply without detection. The flaw was discovered by an internal audit and never exploited, but it undermined the core promise of Zcash: that anyone can independently verify the total supply. The Ironwood upgrade fixes that by introducing a mandatory accounting checkpoint that makes supply manipulation impossible even if a similar bug appears in the future.
The timing isn't great — the crypto market is already jittery, and a forced migration of $1.8 billion adds friction. But the alternative, leaving a known vulnerability in place, was worse. The upgrade is now live, and the migration of funds from the old pool to the new one is expected to take some time.
