Node Enrollment

New nodes join the cluster via a multi-party enrollment ceremony. Unlike the root key ceremony (which establishes the root of trust), enrollment gives a new node its own Ed25519 key.

Protocol

1. Initiate

An authorized author (or the root key) initiates enrollment:

#![allow(unused)]
fn main() {
enrollment.initiate(
    node_id: &NodeId,
    trust_domain: &TrustDomainId,
    authorized_by: &AuthorId,
    total_shares: u8,
    threshold: u8,
    attestation: Option<&AttestationResult>,
)
}

• If attestation is provided, it is verified before enrollment proceeds
• Generates a new Ed25519 KeyPair
• Splits the private key via shamir::split_secret
• Returns EnrollmentId and shares (for distribution to existing nodes)

2. Contribute

Existing nodes contribute shares:

#![allow(unused)]
fn main() {
enrollment.contribute(enrollment_id, share)
}

• Rejects duplicate share indices
• Rejects shares from unknown or completed enrollments
• Returns updated EnrollmentState::Collecting { shares_received, threshold }

3. Complete

#![allow(unused)]
fn main() {
enrollment.complete(enrollment_id)
}

• Requires ≥ threshold shares
• Reconstructs private key via shamir::reconstruct_secret
• Derives VerifyingKey (public key)
• Zeroizes the reconstructed private key
• Generates a membership governance unit ID
• Returns EnrollmentResult { node_id, public_key, key_id, trust_domain, membership_unit_id, attestation }

4. Cancel (if needed)

#![allow(unused)]
fn main() {
enrollment.cancel(enrollment_id)
}

Zeroizes all stored share material. Transitions to Failed state.

Trust model

• The root key (from the Shamir ceremony) authorizes enrollment
• Threshold k out of n existing nodes must contribute shares
• The new node never receives the root key — only its own key
• The enrollment event is recorded as a governance unit in the graph

Attestation

Attestation can be required before enrollment proceeds:

Software attestation generates a SHA-256 hash of the running binary and OS information, bound to a nonce. The verifier checks the quote matches and the signature is valid. This is intentionally weak — it only proves the binary hasn’t been modified at rest, not that the platform is trustworthy.

TPM attestation uses the TPM’s Attestation Identity Key (AIK) to sign a quote of the platform’s boot state. This is cryptographically verifiable and resistant to tampering.