Zcash activates NU7 as Shielded Labs starts quantum-safe research

Zcash activated its NU7 network upgrade at block 3,543,405 on Nov. 6, cutting the target interval between blocks from 75 seconds to 25 and changing how transaction fees are reserved. The activation coincides with Shielded Labs starting a separate research effort to develop cryptography that could protect Zcash against future quantum threats, according to CoinDesk’s report on the NU7 launch.

The upgrade changes Zcash’s block and fee rules now, while post-quantum protection remains research aimed at a future upgrade.

What changes with NU7’s 25-second target?

NU7 reduces the target time between blocks from 75 seconds to 25, but actual block timing takes time to adjust as mining difficulty responds. CoinDesk reported that the first 225 blocks after activation averaged about 39 seconds apart. A shorter target can reduce the wait for a first confirmation, though each exchange or merchant sets its own confirmation requirements.

The upgrade also routes 60% of transaction fees into a public reserve for future mining rewards, with miners receiving the remaining 40%, according to The Block’s report on NU7. The reserved fees are scheduled to begin returning through block rewards at block 8,939,664, expected in 2031. NU7 scales block subsidies and extends the number of blocks between halvings to preserve the existing issuance schedule and 21 million ZEC cap.

NU7 also disables version 4 transactions, which the original Sprout shielded pool depends on. CoinDesk reported that about 12,224 ZEC remained there at activation and became unspendable under the new rules. A possible recovery mechanism has been discussed, but no plan has been approved.

What is Shielded Labs’ quantum-resistance effort?

Shielded Labs announced Epoch on Oct. 1 as a research and engineering project to develop post-quantum cryptography for Zcash. The organization says its three-person cryptography team comprises Chief Cryptographer Ulrich Haböck and engineers Luke Edwards and Suyash Bagad. It is targeting a production-ready implementation by the end of 2027.

Epoch’s first phase is research and design: the team plans to assess candidate cryptographic constructions and develop a proposal in coordination with other Zcash developers. Shielded Labs says it aims for a formally verified implementation with at least 128 bits of security for confidentiality and soundness. The specific approach remains open, and the organization describes this work as a possible basis for a future network upgrade.

Shielded Labs also says Ironwood notes, introduced in an earlier upgrade, are designed to be quantum-recoverable through a future recovery protocol. It explicitly says this does not make Zcash post-quantum today. NU7’s live changes therefore address block timing, fees and transaction validity; Epoch’s cryptographic work remains a separate effort whose design and eventual deployment are still ahead.

References

• CoinDesk’s report on the NU7 launch — coindesk.com
• The Block’s report on NU7 — theblock.co