[eichhorl]

Why

ic-secp256k1 and ic-ed25519 ship the mainnet and PocketIC master public keys of their algorithms, and ic-pub-key uses them to derive keys offline. The mainnet ECDSA keys key_1 and test_key_1 now also exist over secp256r1 (P-256), and PocketIC holds secp256r1 keys too (#11741). But ic-secp256r1 has none of them.

This PR adds the keys and bumps the version, so the crate can be released. ic-pub-key can only use the keys once that release is out (#11894). That's the same order as #7148 before #7194 for the secp256k1 and Ed25519 PocketIC keys.

What

• PublicKey::mainnet_key(MasterPublicKeyId) returns key_1 and test_key_1.
• PublicKey::pocketic_key(PocketIcMasterPublicKeyId) returns the keys PocketIC uses for key_1, test_key_1 and dfx_test_key.
• PublicKey::derive_mainnet_key and PublicKey::derive_pocketic_key derive a canister's public key from those master keys. They are offline equivalents of ecdsa_public_key. For their &CanisterId argument, the crate re-exports ic_principal::Principal as CanisterId, as ic-secp256k1 and ic-ed25519 do.
• hex-literal becomes a regular dependency, to embed the keys, and ic_principal a new one.
• The version goes from 0.2.0 to 0.3.0, with a dated changelog entry, for a release after merging. In-repo dependents use the crate by path without a version, so nothing else changes.
• The cup_explorer README now lists ic-secp256r1 among the crates with hardcoded master keys.

Where the keys come from:

• Mainnet: the CUPs of subnets uzr34 (key_1) and fuqsr (test_key_1). In that same output, the secp256k1, BIP340, Ed25519 and VetKD master keys match the values ic-secp256k1, ic-ed25519 and ic-vetkeys already ship.
• PocketIC: derived the way the StateMachine does it, from PrivateKey::generate_insecure_key_for_testing(42) and the key name.

Tests

• mainnet_keys_round_trip: the mainnet keys round-trip.
• A test derives the PocketIC keys the StateMachine's way and compares them with the hardcoded ones.
• derive_mainnet_key and derive_pocketic_key have known-answer tests for all five keys. The expected keys are what the replica's derive_threshold_public_key (the function that answers ecdsa_public_key) returns for the same master key, canister and path.
• The SLIP-10 retry for nist256p1 (index 33941) is now tested. It's the only branch of the derivation the existing tests didn't reach: it runs when iL >= n, about once in 2^32 steps on P-256. The vector is the one the replica's own key derivation test uses.
• Locally, in the dev container, all of these pass: cargo check, cargo fmt, rust-lint.sh, bazel build //... --nobuild, //bazel:buildifier.check, and the 37 tests from the depth-2 rdeps query (this package, ic-pub-key, rs/crypto, the P-256 basic-sig crate, standalone-sig-verifier, rs/validator).

🤖 Generated with Claude Code

[Copilot]

🔵 Needs a closer look

The mainnet key constants still need independent confirmation against their authoritative source CUPs before release.

No open issues 🎉

What changed in this PR

Adds mainnet and PocketIC P-256 master public keys to ic-secp256r1, preparing a release needed for offline key derivation in ic-pub-key.

Changes:

• Adds key identifiers and constructors for two mainnet and three PocketIC keys.
• Adds mainnet serialization checks and PocketIC derivation tests.
• Prepares version 0.3.0 with dependency and changelog updates.

File	Description
packages/​ic-secp256r1/​tests/​tests.rs	Tests embedded keys and PocketIC derivation.
packages/​ic-secp256r1/​src/​lib.rs	Adds key identifiers, constructors, and constants.
packages/​ic-secp256r1/​CHANGELOG.md	Documents the 0.3.0 release.
packages/​ic-secp256r1/​Cargo.toml	Bumps version and adds the runtime dependency.
packages/​ic-secp256r1/​BUILD.bazel	Aligns Bazel version and dependencies.
Cargo.lock	Records version 0.3.0.

_{Review effort: Balanced}

[pierugo-dfinity]

Verified that the provided mainnet keys match the ones in the live subnets' CUPs.

[Copilot]

🔵 Needs a closer look

The embedded mainnet master keys need independent verification against authenticated CUPs before release.

No open issues 🎉

_{Review effort: Balanced}