Zcash Ironwood pool receives $80M on first day following security upgrade

Zcash users moved around $81 million into the network’s new Ironwood shielded pool during its first day following the activation of the NU6.3 upgrade.

Approximately 176,000 ZEC had entered Ironwood by Wednesday, representing around 5% of the 3.66 million ZEC held in the retired Orchard pool when the upgrade activated.

Ironwood went live Tuesday at block height 3,428,143, introducing a new shielded pool designed to replace Orchard as the network’s primary privacy system.

The upgrade prevents transactions from creating new outputs inside Orchard, meaning the old pool can no longer accept deposits or process transfers between users.

Funds can only leave Orchard through a turnstile mechanism that limits withdrawals to the amount of ZEC that can be verified as having entered the pool. This prevents any hypothetical counterfeit coins from escaping into other parts of the network.

Orchard’s balance has fallen from roughly 3.66 million ZEC to around 3.51 million ZEC since the upgrade, although migration remains voluntary and most shielded funds are still held in the closed pool.

Zcash developers proposed Ironwood after Shielded Labs researcher Taylor Hornby discovered a flaw in Orchard’s zero knowledge circuit that could theoretically have allowed an attacker to create counterfeit ZEC without detection.

The vulnerability had existed since Orchard launched in 2022. Developers patched the flaw through an emergency network upgrade in early June, but Orchard’s privacy features made it impossible to independently confirm whether the bug had previously been exploited.

Developers said there is no evidence that counterfeit ZEC was created and assessed that exploitation was unlikely.

Ironwood uses the patched Orchard circuit alongside formal verification, independent audits, and additional security analysis. The new pool allows node operators to verify that Zcash’s circulating supply does not exceed the amount permitted by the protocol.