Protocol Upgrade v28: Precompiles

[sarahschwartz]

Protocol upgrade v27 is live on ZKsync Era and planned to be completed across all ZK chains in the Elastic Network in the upcoming weeks, marking the start of the rollout process for v28.

Below is a breakdown of what’s included in v28 and how the upgrade will be rolled out.

Key Features

Precompiles

As outlined in the ZIP-11 proposal, this upgrade focuses on optimizing existing precompiles and adding one additional precompile. Previously elliptic curve operations (ECAdd, ECMul, ECPairing) were performed through smart contracts. With this upgrade, these operations will be implemented directly in the ZKVM circuits, significantly reducing the cost for verifying ZK proofs. In one example, the costs were decreased by 94%. Additionally, a precompile for modular exponentiation (ModExp) will be added.

The full list of precompiles includes:

• ✅ ECAdd (Elliptic Curve Addition): This precompile now runs inside the circuit, ensuring the input points are on the curve and handling edge cases like the point at infinity on a pairing-friendly elliptic curve BN256.
• ✅ ECMul (Elliptic Curve Multiplication): This precompile now runs inside the circuit. The circuit implementation performs scalar multiplication with optimizations and correctly handles special cases such as multiplication resulting in the point at infinity.
• ✅ ECPairing (Elliptic Curve Pairing check): This precompile now runs inside the circuit. It supports checking multiple pairs and confirms that input points lie in the correct subgroup.
• ✅ ModExp (Modular Exponentiation): This newly added precompile computes an exponentiation of the form $b^e mod (m)$ for large $b, e, m$. This operation is fundamental in many cryptographic protocols (for example, RSA-based verifications).

From a developer’s perspective, each precompile’s interface and call method remain the same; the upgrade is entirely under the hood. The only change for developers will be cheaper fees for elliptic curve operations, and the ability to use the ModExp precompile.

Contracts on ZKsync Era that already use addresses 0x06, 0x07, 0x08 will continue to function as before. The difference post-V28 is that those calls will execute against the new circuit backed implementations rather than the old in VM computations.

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ZK Gateway Activation

Around the same time ZIP-11 is submitted onchain for a vote, ZIP-10 will also be submitted. ZIP-10 activates Gateway as a settlement layer for the Elastic Network. There is no protocol upgrade needed for this step, as all the code needed for Gateway is already live and audited from v26.

This proposal essentially is just "turning on the switch" to enable Gateway as a settlement layer for the Elastic Network. Note that this does not mean that ZKsync Era will automatically use Gateway for settlement. A separate operation will be required for this.

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Upgrade Timeline

⚠️ All dates below are estimates and may shift. This rollout follows the ZK Nation upgrade process.

Date	Milestone
⏳ May 13	ZKsync Era testnet upgraded to v28. Other ZK chains may choose to upgrade on testnet at this stage.
⏳ May 16	On-chain proposal + voting begins (typical duration: ~10–13 days).
⏳ June 5 June 16	ZKsync Era mainnet upgraded to v28. Other ZK chains may upgrade at this stage.

📢 Progress and announcements will be posted on @ZKsyncDevs on X

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• More details about this protocol upgrade can be found in the ZIP-11 proposal in the ZK Nation forum.