P256 Verifier

Verify passkey signatures on Ethereum mainnet — now live with Fusaka.

Live Demo · EIP-7212

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What This Proves

With Fusaka (Dec 3, 2025), Ethereum gained native P-256 signature verification at 0x0100. This demo shows the full flow:

1. Generate — Mint a P-256 keypair using Web Crypto (same curve as Face ID, YubiKeys)
2. Sign — ECDSA-sign any message you type
3. Verify — Call the precompile on mainnet and get a result in ~3,450 gas

Before Fusaka, this cost 200,000+ gas in Solidity. Now it's a single precompile call.

Why It Matters

Use Case	Benefit
Passkey Wallets	Smart accounts can verify Face ID / Touch ID signatures on-chain
WebAuthn Login	Seedless authentication becomes gas-efficient
Hardware Keys	YubiKey and FIDO2 devices work natively with Ethereum

Quickstart

git clone https://github.com/omarespejel/p256-verifier

cd p256-verifier/frontend

bun install

bun run dev

Requires Bun 1.1+ and a secure context (HTTPS or localhost).

Configuration

Override the default RPC endpoints via environment variables:

VITE_RPC_MAINNET=https://eth.llamarpc.com

VITE_RPC_SEPOLIA=https://rpc.sepolia.org

VITE_RPC_HOLESKY=https://ethereum-holesky.publicnode.com

Deploy

bun run build

Ship frontend/dist/ to Vercel, Netlify, or any static host.

Reuse the Helpers

src/p256.ts exports everything you need:

import { verifyOnChain, buildCalldata } from './p256'

const result = await verifyOnChain({
  messageHash: '0x...',
  r: '0x...', s: '0x...',
  pubX: '0x...', pubY: '0x...'
})

console.log(result.valid, result.gasUsed) // true, 3450n

References

• EIP-7212: Precompile for secp256r1
• Fusaka Upgrade
• WebAuthn Spec

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Built by @espejelomar, Developer Advocate at Starknet Foundation.

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