Evaluate RIP-7212 P-256 precompile on Heima (~707k→~3.4k gas/verify; Pectra-independent)

[hanwencheng]

Summary

Evaluate registering a RIP-7212 secp256r1 (P-256) precompile at 0x100 on Heima. It would cut on-chain P-256 verification from ~707k gas → ~3.4k gas (~200×). Not a blocker for #164 (707k is already ~0.018 HEI/verify at 25 gwei), but the single highest-value chain-side optimization for AgentKeys' passkey/UserOp path — and independent of Pectra (RIP-7212 has shipped on many L2s separately from any mainnet hardfork).

Evidence (measured on Heima mainnet, 2026-06-02)

• Live P256Verifier (pure-Solidity, 0xda5b772f9d6c09abe80414eea908612df9b54749) verifies correctly; one verify(...) costs ~707k gas (measured).
• A full P-256 passkey UserOp (EntryPoint v0.7 + minimal account → live verifier) landed at 730,242 gas total — the verify dominates.
• Heima exposes no precompile at 0x100/0x0b today (Complete real browser-side wiring of the master plane (parent-control web app) #163).

Why it's feasible

• RIP-7212 is a Frontier precompile registration, not new crypto; the p256 crate is already a Heima dependency (per Complete real browser-side wiring of the master plane (parent-control web app) #163). Needs a runtime upgrade.
• Independent of Prague/Pectra (unlike EntryPoint v0.8 — tracked separately).

Cheaper interim option (no chain work)

Swap our pure-Solidity verifier for the Daimo P256Verifier (~421k gas, ~40% cut) — usable in #164 E2 with zero chain changes.

Action

• Scope the Frontier precompile registration + runtime-upgrade cost with the parachain team.
• Decide: precompile (200× win, needs upgrade) vs Daimo swap (40% win, no upgrade) vs status quo (707k, fine today).
• If adopted, Migrate master authority to an ERC-4337 P-256 smart-account (resolves §11 gating findings) #164 E2's verifier reference swaps in one place (kept behind a config interface).

See also

• Migrate master authority to an ERC-4337 P-256 smart-account (resolves §11 gating findings) #164 — ERC-4337 P-256 master (consumer of this).
• docs/plan/chain/erc4337-master-account.md §2 (constraint 5).