Zcash activates Ironwood upgrade sealing Orchard pool

The Zcash network activated a major upgrade on July 28, 2026, sealing its primary private transaction pool and initiating a voluntary migration to a new, more secure system. The move, known as the Ironwood upgrade, directly addresses a previously disclosed bug that could have allowed the creation of counterfeit ZEC tokens within the old Orchard shielded pool.

The upgrade took effect at block height 3,428,143, effectively locking approximately 3.66 million ZEC, worth roughly $1.7 billion, inside the Orchard pool. No new transactions can be created within Orchard, and funds can only exit through a newly enforced "turnstile" mechanism. This accounting rule caps total withdrawals from Orchard at the amount of ZEC that was verifiably deposited into it over its lifetime, preventing any potential counterfeit coins from leaving the sealed pool.

This structural change was prompted by the discovery of a critical flaw in Orchard's proof circuit by Shielded Labs researcher Taylor Hornby in May 2026. The bug, which had been present since Orchard's launch in May 2022, could have enabled an attacker to mint counterfeit ZEC without leaving an on-chain trace. Developers issued an emergency patch...