POST

Session Management

Register request signing key

/api/v2/security/signing-keys

AUTHENTICATIONBearer token · security:writeService ownerdeveloper-platform · identity-accessContract sourceOpenAPISTATUSProduction listed

Purpose and usage

What this endpoint does

When to use it

Call this after generating an Ed25519 key pair, retaining the private key outside Hybrid-Chain, proving possession of the public JWK, and obtaining a fresh step-up grant for key registration.

OUTCOME · Create or advance

What changes

Creates or advances only the request-signing key resource described by this contract after authorization, validation, policy, and idempotency gates pass.

WHY IT MATTERS

Gives people and agents a contract-backed way to advance request-signing key.
Gives human and agentic integrations one discoverable path from service identity and reference data to executable OpenAPI, capability ownership, guides, SDK status, and request-signing controls.

ISOLATION + AUTHORITY

Public service metadata, the OpenAPI document, the capability registry, guides, SDK listings, bearer credentials, step-up grants, and request-signing keys are separate artifacts. Discovery metadata grants no tenant, wallet, custody, payment, settlement, publisher, matching, or trading authority; public signing-key metadata never includes private key material.

BEFORE YOU CALL

Authenticate at the documented boundary: bearer+scope.
Supply the required public_key_jwk (body), proof (body), step_up_token (body) exactly as defined by the live contract.
Resolve whether the caller needs public discovery, bearer authorization, purpose-bound step-up, or RFC 9421 request signing; do not substitute one mechanism for another.

WHAT TO DO NEXT

Re-read the signing-key inventory or target key and confirm the resulting lifecycle state before sending another sensitive request.
After an ambiguous response, reconcile state before retrying; a step-up grant remains bound to its declared purpose and expiry.

AGENT GUIDANCE

Use request-signing key only for the purpose and lifecycle stage described by this operation; do not treat it as authority for an adjacent action.
Supply the required public_key_jwk (body), proof (body), step_up_token (body) exactly as defined by the live contract.
Treat deployment identity, OpenAPI schema, capability readiness, guide narrative, SDK publication, bearer authorization, step-up authorization, and request-signing proof as distinct inputs; none substitutes for another.
After a timeout or conflict, read authoritative state before deciding whether an equivalent retry is safe.

Contract reference

Use the deployed OpenAPI for exact parameters, schemas and security requirements. The tables below provide integration guidance.

Open this operation in OpenAPI

Request and response

Make the request

Examples illustrate integration intent; the referenced OpenAPI operation and component schemas define the executable shape.

PARAMETERS

Headers, path, query, and body

NAMELOCATIONPRESENCETYPE / RULES / PURPOSE

AuthorizationheaderRequired

Bearer tokenCredential containing the security:write scope.EXAMPLEBearer hc_live_…

public_key_jwkbodyRequired

OKP Ed25519 public JWKPublic key with kty=OKP, crv=Ed25519, and a 32-byte unpadded base64url x value.

proofbodyRequired

unpadded base64url Ed25519 signatureProof over the domain-separated canonical registration statement.

step_up_tokenbodyRequired

hcsu_ purpose-bound tokenFresh API_SIGNING_KEY_REGISTRATION authorization.

labelbodyOptional

string · max 160Human-readable device or machine label; defaults to API signing key.

rotated_from_key_idbodyOptional

hck_ identifierExisting key being replaced; it must belong to this identity and client.

REQUEST

JSON body example

{
  "public_key_jwk": {
    "kty": "OKP",
    "crv": "Ed25519",
    "x": "…"
  },
  "proof": "…",
  "step_up_token": "hcsu_…",
  "label": "Production settlement worker",
  "rotated_from_key_id": null
}

STABLE ERROR CODES

Branch on the code, then follow the recovery action

These codes are published by the authoritative gateway contract for this endpoint. Treat message as safe diagnostic text; integrations should branch on code and HTTP status.

STATUSCODEMEANING

400invalid_jsonThe JSON body is malformed or fails the published identity-security schema.

400invalid_security_requestThe session, scope, public key, proof, or purpose-bound security request is invalid.

401invalid_credentialsThe bearer, client assertion, or proof-of-possession credential is invalid.

403step_up_requiredFresh purpose-bound authenticator verification or stronger authority is required.

404signing_key_not_foundThe requested signing-key or workload-client resource was not found.

409security_conflictThe requested identity-security transition conflicts with current state.

503identity_security_unavailableThe authoritative Identity security service is temporarily unavailable.

RESPONSES

Status and payload examples

201Server-assigned public signing key registered after proof of possession.Mutation completed · JSON RESPONSE+

{
  "key_id": "hck_…",
  "algorithm": "ed25519",
  "thumbprint": "f4a5…",
  "label": "Production settlement worker",
  "status": "ACTIVE",
  "rotated_from_key_id": null,
  "created_at": null,
  "expires_at": null,
  "revoked_at": null
}

INTEGRATION DECISION

CALLER ACTION: Accept the returned representation or receipt, then re-read the signing-key inventory or target key and confirm the resulting lifecycle state before sending another sensitive request.
RETRY SAFETY: Do not repeat a successful mutation merely to confirm it. This mutation has no documented idempotent replay contract. Reconcile state before considering another attempt.
STATE RECONCILIATION: Persist returned identifiers, versions, commitments, and receipts. Refresh the application, credential or callback record; compare scope, key identifier, secret-display state, version, and revocation or rotation receipt.

400The JWK or proof of possession is invalid.Request must change · JSON RESPONSE+

{
  "code": "invalid_request",
  "message": "The JWK or proof of possession is invalid."
}

INTEGRATION DECISIONinvalid_request

CALLER ACTION: Rebuild the request from the live OpenAPI operation and correct the rejected method, media type, header, parameter, or body field.
RETRY SAFETY: Do not retry the same invalid request. This mutation has no documented idempotent replay contract. Reconcile state before considering another attempt.
STATE RECONCILIATION: Compare the submitted values with the documented constraints before another call. Refresh the application, credential or callback record; compare scope, key identifier, secret-display state, version, and revocation or rotation receipt.
ESCALATE WHEN: Escalate when a secret-bearing result was lost, key or callback state is ambiguous, or least-privilege scope cannot be established.

401The bearer credential is invalid.Authentication required · JSON RESPONSE+

{
  "code": "invalid_credentials",
  "message": "The bearer credential is invalid."
}

INTEGRATION DECISIONinvalid_credentials

CALLER ACTION: Discard the rejected credential, complete the documented authentication or reassertion flow, and rebuild any request signature with fresh timestamps and nonces.
RETRY SAFETY: Retry only with a newly valid credential and fresh replay-protection values. This mutation has no documented idempotent replay contract. Reconcile state before considering another attempt.
STATE RECONCILIATION: Assume the outcome is unknown only when the connection failed after transmission; otherwise authentication failed before domain work. Refresh the application, credential or callback record; compare scope, key identifier, secret-display state, version, and revocation or rotation receipt.
ESCALATE WHEN: Escalate when a secret-bearing result was lost, key or callback state is ambiguous, or least-privilege scope cannot be established.

403A matching fresh step-up authorization is required.Authority or policy denied · JSON RESPONSE+

{
  "code": "step_up_required",
  "message": "A matching fresh step-up authorization is required."
}

INTEGRATION DECISIONstep_up_required

CALLER ACTION: Verify the exact scope, tenant or workspace membership, owner boundary, step-up purpose, feature policy, and resource eligibility. Never broaden authority automatically.
RETRY SAFETY: Do not retry until the missing authority or policy condition has been deliberately resolved with least privilege.
STATE RECONCILIATION: Confirm the caller and resource resolve to the same authority boundary for developer applications, credentials, signing keys, callbacks, scopes, secrets, and lifecycle receipts.
ESCALATE WHEN: Escalate when a secret-bearing result was lost, key or callback state is ambiguous, or least-privilege scope cannot be established.

409The public key is already registered or the selected predecessor is invalid.State reconciliation required · JSON RESPONSE+

{
  "code": "signing_key_conflict",
  "message": "The public key is already registered or the selected predecessor is invalid."
}

INTEGRATION DECISIONsigning_key_conflict

CALLER ACTION: Stop the mutation sequence and fetch the latest authoritative resource, lifecycle state, version, ETag, reservation, or existing idempotency result.
RETRY SAFETY: Retry only after reconciling the conflict. This mutation has no documented idempotent replay contract. Reconcile state before considering another attempt.
STATE RECONCILIATION: Refresh the application, credential or callback record; compare scope, key identifier, secret-display state, version, and revocation or rotation receipt.
ESCALATE WHEN: Escalate when a secret-bearing result was lost, key or callback state is ambiguous, or least-privilege scope cannot be established.

503Identity security is unavailable.Dependency unavailable or outcome uncertain · JSON RESPONSE+

{
  "code": "identity_security_unavailable",
  "message": "Identity security is unavailable."
}

INTEGRATION DECISIONidentity_security_unavailable

CALLER ACTION: Preserve the exact request and treat the outcome as uncertain until authoritative state proves whether it committed.
RETRY SAFETY: Reconcile before retrying. This mutation has no documented idempotent replay contract. Reconcile state before considering another attempt. Use bounded backoff with jitter.
STATE RECONCILIATION: Refresh the application, credential or callback record; compare scope, key identifier, secret-display state, version, and revocation or rotation receipt.
ESCALATE WHEN: Escalate when a secret-bearing result was lost, key or callback state is ambiguous, or least-privilege scope cannot be established.

OPERATIONAL NOTES

Security and lifecycle guarantees

Sign key-sorted compact JSON containing algorithm=ed25519, the authenticated client_id, label, public_key_jwk, and rotated_from_key_id, prefixed by hybrid-chain/api-signing-key-registration/v1 plus a NUL byte.
Hybrid-Chain assigns key_id after verifying possession; clients do not submit a key identifier.
Sensitive V2 mutations subsequently require the bearer plus an RFC 9421 Ed25519 HTTP Message Signature and RFC 9530 Content-Digest.

UPGRADING FROM V1

Legacy calls replaced by this operation

If you maintain an older integration, use this map to find the V2 replacement. Do not translate the old request field-for-field: rebuild it from the V2 parameters and schemas above because identity, authorization, replay protection, and response semantics may have changed.

POST/api/v1/sessions/newSESSION: Create new API Key

Reference version and availability details

This route is implemented in canonical gateway source and appears in the production OpenAPI snapshot observed 2026-10-02T23:27:55.510Z. Authentication, tenant, feature, venue, and market policy still apply.

Verify the exact production OpenAPI operation Return to the V2 directory