How the RRF and RCAN Work Together¶

RCAN protocol §21 · Stable

Two independent standards designed to work together. Use either alone or both together for globally identifiable, cryptographically verifiable robot identity.

Two Different Things, Designed to Compose¶

RRF — The Registry

Assigns permanent RRNs
Any robot can register
No software required
Neutral, independent governance

RCAN — The Protocol

Defines how robots identify, sign, and prove behavior
Any language or runtime
ML-DSA-65 message signing (NIST FIPS 204)
Hierarchical URIs (RURIs)
See the live compatibility matrix · 4 entity types (RRN/RCN/RMN/RHN)
Registry-relevant features: federated consent protocol (FEDERATION_SYNC, cross-registry JWT trust); human identity LoA 1/2/3 (FIDO2, min_loa_for_control); robot identity revocation API (revocation_status); bandwidth-constrained transports (LoRa, BLE, CBOR)

Used together: a robot becomes globally identifiable via its RRN and cryptographically verifiable via its RCAN keys. Anyone can look up the robot, resolve its RURI, and verify that its signed messages are authentic.

The Identifier Relationship¶

RRN — RRN-000000000001

Opaque, permanent, registry-assigned. Stable across renames, re-deployments, ownership transfers.

RURI — rcan://rcan.dev/myorg/my-robot-model/unit-001

Hierarchical, protocol-level address. Human-readable. Scoped to an organization and model.

Link — A registered robot can associate its RURI with its RRN. The registry stores the mapping.

Lookup:

GET /api/v1/resolve?ruri=rcan://...

Returns the RRN if the RURI is registered.

Ownership Proof Flow¶

The challenge/sign/verify handshake from RCAN §21. A robot proves it holds the private key for its RURI without transmitting that key.

Step 1 — Request a challenge:

POST /api/v1/challenge
{ "ruri": "rcan://rcan.dev/myorg/mybot/unit1" }

Step 2 — Registry returns a 32-byte nonce:

{ "nonce": "a3f8...", "expires_at": "2026-03-12T00:05:00Z" }

Step 3 — Robot signs nonce with ML-DSA-65 key:

# Same ML-DSA-65 key used for RCAN message signing
signature = ml_dsa_sign(private_key, nonce)

Step 4 — Submit proof:

POST /api/v1/verify
{ "ruri": "...", "nonce": "...", "signature": "...", "public_key": "..." }

Step 5 — Registry verifies → robot promoted to "verified" tier:

{ "status": "verified", "rrn": "RRN-000000000005", "verified_at": "2026-03-12T00:00:42Z" }

Using rcan-py¶

from rcan import RCANClient, MessageSigner

signer = MessageSigner(private_key_path="~/.rcan/key.pem")
client = RCANClient(ruri="rcan://rcan.dev/myorg/mybot/unit1")

# Register with the Robot Registry Foundation
result = client.registry_register(
    registry_url="https://robotregistryfoundation.org/api/v1",
    metadata={"name": "My Robot", "manufacturer": "MyOrg"}
)
print(result.rrn)  # "RRN-000000000001"

rcan-py handles the full challenge/verify handshake automatically.

Choose Your Path¶

Without RCAN

Submit the form, get an RRN. No software to install, no keys to manage. Works for any robot — commercial, research, homebrew.

Verification tier: community — suitable for most use cases. The robot is registered and globally identifiable.

Register now

With RCAN

If your robot runs RCAN, prove ownership cryptographically and automatically upgrade to verified or manufacturer tier.

The registry stores your public key. Anyone can verify your robot's signed messages without contacting you directly.

Get RCAN

§19 INVOKE — Remote Skill Execution¶

RCAN §19 defines how a principal triggers a named skill on a robot and receives a structured result. Robots registered with the RRF can expose INVOKE endpoints, allowing authorized callers to execute skills by RURI + RRN.

INVOKE request:

{
  "type": "INVOKE",
  "skill": "pick_and_place",
  "params": { "target": "red_cube" },
  "timeout_ms": 5000,
  "msg_id": "invoke_abc123"
}

INVOKE_RESULT (success):

{
  "type": "INVOKE_RESULT",
  "skill": "pick_and_place",
  "status": "success",
  "reply_to": "invoke_abc123",
  "duration_ms": 1230
}

INVOKE_RESULT (failure):

{
  "type": "INVOKE_RESULT",
  "skill": "pick_and_place",
  "status": "failure",
  "reply_to": "invoke_abc123",
  "duration_ms": 312,
  "error": { "code": 7006, "name": "SkillFailed", "message": "Gripper could not secure the target object" }
}

RBAC enforcement: INVOKE messages are subject to RCAN role-based access control. A principal must hold the required capability lease for the target skill. RRF-registered robots can publish their skill manifests publicly, enabling third-party orchestration.

Full §19 INVOKE specification

§20 Telemetry Field Registry¶

RCAN §20 defines standard telemetry objects — joint state, robot state, and Prometheus exposition — that robots emit on a predictable cadence. RRF-registered robots may publish a telemetry endpoint URL in their registry record so observers can subscribe without prior coordination.

Joint telemetry object:

{
  "joint": "shoulder_pan",
  "position_rad": 0.785,
  "velocity_rad_s": 0.02,
  "effort_nm": 0.41,
  "temperature_c": 38.5,
  "error_flags": 0,
  "timestamp_us": 1741737600000000
}

Prometheus exposition (excerpt):

rcan_acb_position_rad{joint="shoulder_pan",ruri="rcan://robot.local"} 0.785
rcan_acb_velocity_rad_s{joint="shoulder_pan",ruri="rcan://robot.local"} 0.02
rcan_robot_battery_v{ruri="rcan://robot.local"} 14.2
rcan_robot_uptime_ms{ruri="rcan://robot.local"} 3600000

RRF integration: A robot's registry record can include a telemetry_url field. This lets dashboards and monitoring systems discover the Prometheus scrape endpoint directly from the RRN lookup — no separate service discovery required.

Full §20 Telemetry Field Registry

OpenCastor — RCAN-Conformant Implementation¶

OpenCastor is an open-source Python framework for building RCAN-conformant robots. It implements the full RCAN stack including RBAC, ML-DSA-65 signing (NIST FIPS 204), safety invariants, and §21 registry integration.

Full RCAN protocol conformance · ML-DSA-65 PQ signing · RBAC + capability leases · Virtual FS with safety kernel · 4-type registry (RRN/RCN/RMN/RHN) · RRF §21 registry integration · Runs on Raspberry Pi, x86, and more.

Go deeper¶

Looking for the live registry search? See robotregistryfoundation.org/registry.