Zcash activated its Ironwood upgrade on Tuesday at block height 3,428,143, introducing a new shielded pool for the privacy blockchain. The upgrade follows concerns about the soundness of Zcash's earlier Orchard pool, which will now be restricted to support only withdrawals. Orchard was previously Zcash's primary privacy pool, accounting for nearly 88% of the blockchain's shielded token supply at its height, with older shield pools Sapling and Sprout making up the rest. The vulnerability in Orchard, discovered in late May by Shielded Labs researcher Taylor Hornby, involved a flaw in its zero-knowledge circuit that could theoretically have allowed an attacker to create counterfeit ZEC without detection. Zcash developers prioritized patching the pool and launching a more mathematically sound and secure alternative through the NU6.3 network upgrade.
Migration Data Shows 40,207 ZEC Moved to Ironwood Pool
According to a migration tracker, some 40,207 ZEC have migrated into Ironwood, while about 3.6 million tokens remain in Orchard. Removing funds from Orchard will remain discretionary. ZEC dropped about 9% on Tuesday to $460 before recovering to about $475, according to The Block's price page. The token tanked over 50% after the Orchard bug was disclosed. ZEC rallied hard beginning in September of last year, climbing from about $45 to a high of around $700 by year's end.
Orchard Vulnerability Discovered in Late May
The vulnerability in Orchard was discovered in late May by Shielded Labs researcher Taylor Hornby. The flaw involved Orchard's zero-knowledge circuit that could theoretically have allowed an attacker to create counterfeit ZEC without detection. Analysts have said Orchard, launched in 2022, was likely not exploited and found no evidence of it occurring. An emergency soft fork temporarily disabled Orchard activity on June 2, with a hard fork applying corrected circuit code on June 3.
ZODL Engineers Contributed 82% of Protocol Changes
Ironwood represents a unified effort across Zcash's decentralized developer ecosystem, including efforts from the Zcash Open Development Lab (ZODL), Project Tachyon, Valar Group, the Zcash Foundation, and Shielded Labs. Shielded Labs, co-founded by renowned cryptographer Zooko Wilcox, drove the initial proposal to restore supply verifiability. ZODL Executive Director Josh Swihart said 14 ZODL engineers accounted for 82% of the merged changes to Zcash's protocol and wallet repos as part of the Orchard fix and migration to Ironwood. Swihart said Monday on X that Orchard was fixed in 5 days and replaced in 60.
Ironwood Pool Incorporates Formal Verification and Quantum-Recoverable Notes
Ironwood reuses the fixed Orchard circuit and its Halo 2 proof system, along with some minor modifications. The pool has been formally verified, providing a stronger assurance it will perform as designed under all possible circumstances. Zcash co-founder Sean Bowe said on X that a cross-team collaboration has just changed Zcash's history forever, eliminating all sources of undetectable counterfeiting bugs from the new Ironwood protocol. The new pool also incorporates quantum-recoverable notes under ZIP 2005, offering a future recovery path if quantum computing advances compromise current cryptography, ZODL noted. The upgrade also installs a turnstile that will limit the amount of funds that can exit Orchard and enables independent auditing of ZEC's circulating supply, helping ensure the counterfeiting bug did not break Zcash's 21 million coin cap.
FAQ
What is the Zcash Ironwood upgrade that activated on Tuesday?
The Ironwood upgrade activated on Tuesday at block height 3,428,143 as part of the NU6.3 network upgrade, introducing a new shielded pool for Zcash following concerns about the soundness of the earlier Orchard pool.
Why did Zcash developers create the Ironwood pool?
Zcash developers created Ironwood after Shielded Labs researcher Taylor Hornby discovered a vulnerability in late May involving a flaw in Orchard's zero-knowledge circuit that could theoretically have allowed an attacker to create counterfeit ZEC without detection.
How much ZEC has migrated from Orchard to Ironwood?
According to a migration tracker, some 40,207 ZEC have migrated into Ironwood, while about 3.6 million tokens remain in Orchard.
