Zcash Seals 1.7 Billion Pool After Counterfeiting Bug But Holders Are in No Rush to Leave

Just one day after Zcash sealed its largest private funds pool following the discovery of a four-year counterfeiting vulnerability, only about 5 percent of holders have moved their coins to safety. The remaining 95 percent sit in a pool that can no longer accept new deposits — and nobody knows exactly how long it will take for them to find the exit.

By Carlos Martinez | July 29, 2026

The Hook

Imagine discovering that the vault at your local bank had a hidden flaw in its lock mechanism for four years. Nobody can prove anyone broke in, but nobody can prove they did not either. That is essentially what happened to Zcash, one of the cryptocurrency world’s leading privacy-focused coins.

On Tuesday, July 28, Zcash activated its Ironwood upgrade — formally known as NU6.3 — at block 3,428,143. The upgrade permanently closed the Orchard shielded pool, which held about 3.66 million ZEC worth roughly 1.7 billion at current prices. A new pool called Ironwood opened with zero coins, and every holder must now voluntarily move their funds across a one-way bridge called a turnstile.

The reason? A bug discovered on May 29 by Shielded Labs researcher Taylor Hornby. The flaw, hidden inside Orchard’s proof circuit since the pool launched in May 2022, could have allowed someone to create counterfeit ZEC without leaving any trace on the blockchain. In the world of privacy coins, where transactions are designed to be invisible, that is the worst possible scenario.

On-Chain Evidence

The numbers tell an interesting story about how Zcash holders are responding to the crisis. According to the Ironwood migration tracker, roughly 176,000 ZEC — worth about 81 million — had crossed into the new pool within the first 24 hours. That sounds like a lot, but it represents only about 5 percent of what was sitting in Orchard.

The Orchard pool’s balance has dropped from 3.66 million ZEC to approximately 3.51 million, with around 46,000 ZEC crossing over in the past day alone. At this pace, a full migration could take weeks or even months.

Zcash organizes its funds into separate compartments called pools, each representing a generation of privacy technology. The transparent pool works like Bitcoin, with every balance and transaction visible on the chain, and holds about 12.5 million ZEC. The older Sapling pool, introduced in 2018, holds roughly 582,000 ZEC. Orchard, which arrived in 2022 and was the newest pool until this week, held the lion’s share of private funds.

The Core Conflict

Here is the central tension: the bug existed for four full years. While evidence suggests it was never exploited — the Orchard pool’s balance grew steadily through that period, including during last year’s price rally when cashing out counterfeit coins would have been most profitable — nobody can definitively prove that no fake coins were created. That is the nature of zero-knowledge proofs. They verify transactions without revealing details, but they also mean the chain holds no record of whether counterfeit coins were minted.

The turnstile mechanism is Zcash’s answer to this uncertainty. Think of it like a toll booth on the exit ramp of a parking garage. The booth knows exactly how many cars entered the garage, and it will not let more than that number leave. Even if someone somehow parked counterfeit cars inside, those cars cannot get out.

Money crossing into or out of a shielded pool is public information, even when the transactions inside the pool are completely private. So the network already knows precisely how much real ZEC went into Orchard — and it will not release a single coin more than that amount.

Market Implications

The market reaction has been measured but not panicked. ZEC traded near 463 ahead of the switch, down 8 percent on the day of the upgrade and 15 percent over the week. However, the coin remains up roughly tenfold over the past year, suggesting that long-term holders are not treating this as a death blow to the project.

Ironwood also brings two significant improvements that Orchard never had. First, the record each coin leaves on the chain is built to stay recoverable even if quantum computers eventually break today’s cryptography — a feature specified under ZIP 2005 and active from the very first block. Second, the pool’s proof circuit is undergoing formal verification, which produces a mathematical guarantee that the software behaves correctly in every possible scenario, not just the cases that testers thought to check.

Think of it like upgrading from a lock that was tested by trying random keys to one that comes with a mathematical proof that no key exists except the right ones.

The Verdict

The number to watch from here is how fast those 3.66 million ZEC actually move. Migration is entirely voluntary and user-driven. Wallets, exchanges, and individual holders all need to update their software and initiate transfers at their own pace. Until that happens, the bulk of Zcash’s private supply sits in a pool that has been closed to new money since Tuesday.

For everyday investors, the Zcash Ironwood upgrade is a reminder that even the most sophisticated privacy technology is not immune to human error. A single bug in a proof circuit went undetected for four years. The system’s response — sealing the pool, forcing a controlled migration, and adding formal verification — may well become a textbook case for how blockchain networks handle security crises.

But the slow migration rate also raises a question: if 95 percent of holders are in no rush to move their coins to the supposedly safer pool, does that signal confidence that the bug was never exploited, or simply the inertia of a fragmented user base? The answer may not be clear for months.

Disclaimer: This article is for informational purposes only and does not constitute financial advice. Cryptocurrency investments carry significant risk. Always conduct your own research before making investment decisions.