EIP-7951 — secp256r1 Precompile

EIP-7951secp256r1 Precompile

Runnable

Live on the hosted MCP — free on Fusaka (mainnet today) and Amsterdam.

Fusaka (mainnet) · AmsterdamRuns withrun_bytecode

Website twin: exploration on feelyourprotocol.org

What became possible

Why add a secp256r1 precompile?

EIP-7951 exposes P-256 (the curve behind Apple/Android passkeys and WebAuthn) at address 0x100. Contracts can verify device-native signatures on-chain. The precompile is live on Fusaka (current mainnet EL).

The MCP server runs caller-supplied bytecode that CALLs the precompile with five 32-byte fields: message hash, r, s, public key x, public key y. A valid signature returns 0x01 (32 bytes). Invalid payloads fail or return empty data — your agent can explore both. There is no dedicated precompile input tool; construct a CALL to 0x100.

Try asking your agent

The hosted MCP is live (Connect). Copy a prompt into your agent — each quote is self-contained. Fusaka is the run target.

Job

Fusaka

On Fusaka, CALL precompile 0x100 with a standard valid P-256 test vector (message hash, r, s, pubX, pubY) — does it return 0x01?

Look for0x01 for a valid signature

Agent will likely call run_bytecode

Lesson

Fusaka

On Fusaka, run the same secp256r1 CALL twice — once with a valid P-256 vector and once with r incremented by 1 — what does each return?

Look for0x01 versus empty or failing data

Agent will likely call run_bytecode

Check

Fusaka

On Fusaka, CALL 0x100 with a valid P-256 vector — how much gas does the verification use?

Look forgasUsed for the CALL to 0x100

Agent will likely call run_bytecode

What the server does

1. 1

   Discover support

   Confirm the 7951 catalog entry; read the input layout.

2. 2

   Run bytecode

   Execute CALL bytecode on fusaka.

Fork caveat

Available on Fusaka (mainnet) and later lineage forks. Teaching is valid vs invalid return data, not a gas delta vs Pectra. The probe may list a Pectra→Fusaka pair (activation); that is “precompile missing vs present,” not a pricing lesson.

Twins and spec

Website exploration

EIP-7951 on feelyourprotocol.org

Canonical spec

EIP-7951

Fork page

Current mainnet — Fusaka

EIP catalogue

Coverage

EIP-7951 MCP Catalogue Changelog

EIP-7951 MCP Catalogue Changelog

1. v0.32026-09-17Mainnet-adoption prompts; CALL-to-0x100 path; valid vs invalid, not a Pectra gas compare.
2. v0.22026-09-02Status is public-launch ready — no local / self-host framing.
3. v0.12026-08-31Initial catalogue page — P-256 verification on 0x100, twin link.