Zcash Preparing for NU 8 Upgrade: 4x Block Capacity Expansion, Privacy Transactions Target 200 TPS, Quantum-Resistant Solutions Advance Simultaneously

Author: TechFlow

On November 10, 2026, Zcash community developer ValarDragon proposed the NU 8 network upgrade vision in a Zcash official forum proposal post, with the target window set for late January 2027. The proposal covers privacy pool iterations, block expansion, and cryptographic defense updates.

The core of the proposal lies in launching the new Tachyon shielded pool, increasing the maximum block limit to 8MB, and introducing post-quantum signature opcodes. If this architecture is implemented, Zcash shielded transaction throughput is expected to reach 200 TPS, aiming to break through the performance bottlenecks long faced by privacy public chains.

Block Expansion to 8MB Sparks Light Client Bandwidth Controversy

Block expansion is the central topic of this discussion. The current Zcash network maintains a high-frequency block production pace and a 2MB block limit, with the community previously proposing a block expansion ZIP draft targeting 3MB. ValarDragon believes that leveraging underlying optimizations, the network can directly jump to an 8MB capacity.

Compared to the current 2MB specification, the 8MB limit increases block capacity by four times, and by approximately 2.67 times compared to the 3MB draft, providing a computational foundation to achieve 200 TPS. However, this requires full nodes to process more data within a single block production window, thereby raising hardware thresholds and continuous bandwidth requirements.

Core engineer str4d has raised objections regarding this. str4d emphasized that the specifications for out-of-band communication (OOB) and private information retrieval (PIR) relied upon by light wallets have not yet been established. Directly pushing forward with an 8MB expansion would increase the data synchronization burden on mobile light clients, requiring a trade-off between bandwidth and throughput.

Dual-Track Construction of Post-Quantum Defense System for Shielded and Transparent Layers

In terms of security design, the proposal outlines a layered defense mechanism. The newly launched Tachyon shielded pool adopts the ML-KEM ciphertext encapsulation mechanism at its core, building an unconditional post-quantum privacy system. This ensures that even if future quantum computing possesses cracking capabilities, it will be unable to decrypt past on-chain transaction graphs.

For transparent addresses, the proposal plans to add opcodes supporting 128-bit and 192-bit SPHINCS signatures (such as SLH-DSA). This design aims to provide proactive post-quantum security protection for scenarios such as transparent assets that have not migrated to the shielded pool and the Ironwood disaster recovery path.

Transaction Format Upgrade and Consensus Branch ID Change Controversy

At the transaction structure level, the proposal recommends integrating the ZIP 248 specification. This specification reconstructs the extensibility of the transaction format, capable of eliminating metadata fingerprints exposed by hardware wallets when adding new shielded pools, thereby blocking off-chain analysis paths that track transactions through device signature differences.

The proposal advocates canceling the mechanism that mandates changing the Consensus Branch ID with every upgrade, in order to reduce adaptation fractures caused by forks on the wallet ecosystem. str4d warns that this parameter serves as a key defensive barrier against cross-fork transaction replay attacks, and an alternative anti-replay mechanism must be established before its abolition.

Asset Pool Phase-Out Governance and Milestone Constraints

Regarding asset pool lifecycle management, the proposal does not adopt the hard freeze measures used for the Sprout pool during the NU 7 period. Instead, it sets a specific timestamp at the protocol level for the Sapling pool to stop new deposits. Existing users can still freely initiate transfers and withdrawals within this pool, preserving ample migration buffer time.

The proposal also adjusts the Network Sustainability Mechanism (NSM) redistribution node to near the point where Zcash completes its 7th cumulative halving. Based on a 4-year halving cycle, this adjustment will delay tail emission pressure by 4 to 8 years. With only about two and a half months remaining until late January 2027, the technical roadmap can refer to the official Tachyon roadmap.

Currently, ValarDragon's proposal is in the open technical deliberation stage on the official forum. The development team will subsequently need to conduct rigorous technical reviews around PIR specifications and alternative anti-replay mechanisms. Once all parties reach a code consensus, the proposal will formally enter the standard finalization phase and be submitted to the community for NU 8 governance voting.