Zcash is approaching a network upgrade that will effectively lock the remaining funds in its oldest shielded pool unless holders move them in time. As of Thursday morning, about 12,226 ZEC remained in the Sprout pool, a balance worth roughly $16 million at a price of $1,300 per coin.

The deadline is tied to the NU7 upgrade, which will stop accepting the transaction format required to spend Sprout coins. Once that change takes effect, any ZEC left in Sprout will become unspendable under the new network rules, even if the owner still controls the private keys.

Balances fell sharply, but much remains

The amount still sitting in Sprout has dropped over the past week, falling from around 22,263 ZEC to 12,226 ZEC by Thursday morning. The biggest move came on Sunday, when roughly 9,094 ZEC left the pool. Only 40 ZEC followed on Wednesday.

Because withdrawals were still underway, the final amount frozen could end up below the Thursday estimate. At the quoted price, however, the remaining balance was still substantial enough to put millions of dollars at stake before the upgrade activates.

Why NU7 makes Sprout funds unspendable

Zcash uses shielded pools to obscure who sent funds, who received them and how much was transferred. Sprout, launched with the network in October 2016, was the first of these privacy systems and has since been replaced by newer shielded pools built on later generations of the technology.

NU7 will retire the older transaction path used by Sprout. Specifically, the upgrade will reject version-4 transactions, which are the only type capable of spending coins held in that pool. That means any balance not moved beforehand will no longer be spendable after the upgrade under the updated consensus rules.

Old software carries ongoing costs

The case for retiring Sprout is not only about low usage. According to ZIP 2003, continuing to support the legacy pool adds software complexity and security risk to the code that verifies Zcash payments.

Removing that machinery is part of a broader cleanup in NU7. The same upgrade also reduces the target block time from 75 seconds to 25 seconds, a change intended to shorten the expected wait for confirmations on the network.

What holders can still verify

One practical clue for anyone reviewing old wallet records is the address format. Sprout addresses begin with “zc,” which may help identify whether dormant funds are affected by the deadline.

Even if coins are left behind, they will still count as part of Zcash’s issued supply. ZIP 2003 does leave open the possibility that access could be restored in a future upgrade, but it also warns that spending may never be re-enabled. For now, the confirmed next step is the NU7 activation, after which version-4 transactions will no longer be accepted.

Source: www.coindesk.com