Zcash NU7 upgrade to freeze Sprout privacy pool funds

The upcoming Zcash NU7 network upgrade aims to freeze the Sprout shielded pool, effectively preventing users from spending remaining funds even if they retain their private keys. This move is designed to reduce the network's attack surface by phasing out legacy cryptographic code in favor of more efficient designs like Sapling and Orchard.

As of mid-October, approximately 22,309 ZEC remained in the Sprout pool. Under the proposed ZIP 2003 improvement proposal, the network will reject version 4 transactions, which are required for Sprout transfers. While the coins will remain part of the total issued supply, they will become unspendable because newer transaction formats do not support the Sprout protocol.

The mainnet activation date is currently undecided, though developers are targeting November 5, contingent on testnet results. Users holding legacy ZEC are advised to migrate their balances to supported pools before the upgrade, as current wallet software migration processes may not automatically include Sprout spending keys.