Zcash’s upcoming NU7 upgrade will make approximately $16 million in ZEC remaining in the old Sprout privacy pool unspendable, even if its owners hold their private keys.
According to a report by CoinDesk based on ZecStats records, approximately 12,226 ZEC remained in the Sprout pool on the morning of November 5. The balance had been approximately 22,263 ZEC a week earlier, with most of the reduction coming from an outflow of approximately 9,094 ZEC on Sunday; only 40 ZEC left the pool on Wednesday.
Sprout is Zcash’s oldest privacy pool, launched in 2016. While the newer pools the network developed in subsequent years use different technology, the upcoming change directly affects old balances left in Sprout.
The deadline depends on block height, not the clock
NU7 is scheduled to activate at block 3,543,405. At 08:24 Turkey time on November 5, the network was at block 3,542,391. Based on the target time of 75 seconds per block, approximately 21 hours remained until the upgrade at the time of that measurement.
This calculation suggests activation could take place at around 05:30 Turkey time on November 6. The exact time will depend on how quickly miners produce blocks.
Why won’t private key holders be able to spend their coins?
According to ZIP 2003, which defines the change, NU7 will reject version 4 transactions. Since this is the only transaction format that allows Sprout coins to be spent, any balances remaining in the pool at activation will be unspendable under the new network rules.
Addresses beginning with “zc” in old wallet records may help identify Sprout balances. The publicly reported total pool balance does not show who owns the coins or how many are in wallets whose keys have been lost.
At $1,300 per ZEC, the current balance is worth approximately $16 million. Outflows from the pool before the upgrade could reduce the amount that becomes unspendable.
There is no guarantee access will be restored
The coins remaining in the pool will continue to be part of Zcash’s total issued supply. ZIP 2003 does not rule out the possibility that access could be restored with another upgrade in the future, but it also warns that spending may never be re-enabled.
Maintaining the old Sprout transaction infrastructure adds complexity and security risk to payment verification software. NU7 will also reduce the target time between blocks from 75 seconds to 25 seconds, shortening the expected wait for transaction confirmations.
Not investment advice.