Zcash Activates NU7, Cutting Target Block Time to 25 Seconds

Zcash activated its NU7 network upgrade at block 3,543,405 on Nov. 5, cutting the target time between blocks from 75 seconds to 25 seconds. The change is designed to speed confirmations for private payments, according to CoinDesk’s report on the activation.

Block production had not yet reached the new target immediately after activation. CoinDesk reported that the next 225 blocks averaged about 39 seconds apart by 04:59 UTC on Nov. 6, as mining difficulty adjusted.

How does NU7 change shielded payment capacity?

NU7 raises the target block rate while limiting shielded transaction activity per block, reducing the amount of blockchain data light wallets may need to scan. The Zcash Foundation said the limits are expected to more than double Orchard throughput, from 2.9 to 6.6 transactions per second, and cut worst-case wallet sync bandwidth by about 37% in its Zebra 7.0.0 release notes.

Those figures describe capacity and sync limits, not a guarantee of transaction speed for every user. CoinDesk reported that exchanges and other services set their own confirmation requirements, which affect when a payment can be used.

What happens to transaction fees and old Sprout funds?

NU7 routes 60% of each block’s transaction fees into a reserve and leaves the other 40% with miners, the Foundation said. The reserve is scheduled to begin contributing to future block rewards at height 8,939,664; the Foundation said the upgrade keeps the 21 million ZEC supply cap and existing halving schedule unchanged.

The upgrade also disables version 4 transactions. Because Zcash’s original Sprout pool relies on that format, funds remaining there become unspendable, according to the Foundation’s release notes.

Sources

• CoinDesk’s report on the activation — coindesk.com
• Zebra 7.0.0 release notes — forum.zcashcommunity.com