Zcash activated its NU7 upgrade early Friday, cutting the target time between blocks from 75 seconds to 25 and setting up private payments to confirm three times faster.
The upgrade went live at block 3,543,405, mined at 02:34 UTC. By 04:59 UTC, the network had produced another 225 blocks, averaging about 39 seconds apart, according to ZecStats. Mining difficulty, which determines how hard it is to produce a block, was still adjusting toward the faster pace.
Zcash lets people send money while hiding the sender, recipient and amount. Faster confirmations could make those payments easier to use at a shop, through an exchange or when moving funds between blockchains.
A merchant could see a payment’s first confirmation in about 25 seconds on average. An exchange requiring three confirmations could cut its expected wait from nearly four minutes to about 75 seconds.
Each service sets its own requirements, so how quickly customers can use their money will also depend on the service handling it.
How it works
Keeping miners working together at that pace required more than changing the clock.
When a miner finds a block, other miners need to receive and check it before starting work on the next one. During that delay, another miner can produce a competing block that the network eventually discards — and these shorter intervals leave less time to catch up.
Zakura, Zcash node software built by network developers Valar Group and Project Tachyon, tested 25-second blocks on 80 computers spread across 11 regions, with each block filled with transactions. Under those demanding conditions, 3.43% of mined blocks were discarded, compared with 1.57% at the old 75-second pace.
Its engineers also reduced repeated work. The software checks a transaction when it first arrives, then remembers parts of that check so it does not have to start from scratch when the transaction appears in a block. Checks that depend on the latest account balances and blockchain history still run again.
NU7 also limits how much private transaction activity can fit into each block. Wallets must scan the blockchain to find payments meant for them, and someone flooding it with transactions can force every wallet to do more work.
The limits reduce the worst-case daily download burden from 271 megabytes to 169, according to the upgrade specification. Combined with more frequent blocks, the specification estimates capacity for simple private payments could more than double, from about three a second to more than six.
