Zcash activates Ironwood and seals the Orchard pool

Zcash activated its Ironwood network upgrade at block 3,428,143, sealing the Orchard shielded pool and opening a replacement that starts empty. Orchard held about 3.66 million ZEC at the point it closed.

The upgrade answers a counterfeiting vulnerability that Shielded Labs researcher Taylor Hornby found in Orchard, an infinity bug that could in principle have allowed undetectable creation of counterfeit ZEC inside the pool. Because the flaw made supply unverifiable rather than provably exploited, the response was to stop the pool accepting new value rather than to patch it in place.

Funds can no longer be sent or received inside Orchard. They leave only through the existing turnstile, which enforces that no more ZEC exits the pool than legitimately entered it. The new pool adds quantum-recoverable notes and formally verified cryptography.

Sealing a pool converts an unbounded supply risk into a bounded one: whatever was counterfeited, if anything, can no longer grow, and the turnstile caps what can escape.