OSCORE and EDHOC Security Workbench

Step through EDHOC key establishment, OSCORE context derivation, protected CoAP traffic, proxy visibility, and replay checks

animation
oscore
edhoc
coap-security
constrained-iot
privacy
Interactive OSCORE and EDHOC animation for learning constrained IoT key establishment, object security for CoAP, proxy-safe protected fields, visible routing metadata, and replay-window behavior.
Interactive Animation CoAP Security EDHOC + OSCORE

OSCORE and EDHOC Security Workbench

Watch constrained endpoints establish fresh security material with EDHOC, derive an OSCORE context, then send protected CoAP messages through a proxy that can route traffic without reading the application data.

EDHOC message 1Current phase
Not derivedOSCORE context
Routing metadataProxy view
Low riskLearning diagnosis
Goal
Separate key establishment, OSCORE context derivation, protected CoAP content, and visible routing metadata.
Try
Compare proxy-safe OSCORE, combined setup, replay attempts, and hop-by-hop-only protection.
Watch
Use Step to follow message_1, message_2, message_3, context derivation, request, and response.
Check
Decide whether the proxy can read payload fields and whether stale sequence numbers are rejected.

EDHOC to OSCORE Message Flow

The client and server run EDHOC through a proxy, derive an OSCORE context, then protect CoAP application fields while leaving only routing metadata visible.

Sensor ClientEDHOC initiator and OSCORE sender
Forward Proxyroutes outer fields only
Resource ServerEDHOC responder and protected resource
EDHOC message_1: the initiator sends method/cipher-suite choices, a connection identifier, and ephemeral key material.
Exporter Secretwaiting for EDHOC
Sender and Recipient IDsnot assigned
AEAD Keysnot derived
Common IV + Partial IVnot in use

Protected by OSCORE

    Visible for Routing and Delivery

      Protocol Trace

      Start: EDHOC authenticates the endpoints and establishes fresh material before OSCORE protects CoAP objects.

      Diagnosis

      RPK/certCredential mode
      32 messagesReplay window
      outer fieldsProxy access
      3 + 1Setup shape

      The proxy can forward the message using outer fields, but the application request and response remain protected end to end by OSCORE.

      Open secretnone yet
      Proxy clueOuter options support forwarding; inner fields are for endpoints.
      Replay clueSender sequence numbers must not repeat, and recipients check a replay window.
      Quick Reference
      • EDHOC: compact authenticated Diffie-Hellman over COSE for constrained devices. It gives endpoints fresh key material and supports forward secrecy.
      • OSCORE: object security for CoAP. It protects the CoAP application object rather than only the transport connection.
      • Inner fields: CoAP code, payload, and protected options intended for the endpoint.
      • Outer fields: fields needed by the network path, such as forwarding information and the OSCORE option marker.
      How To Debug
      • If a proxy must route the message, check whether the required routing information is deliberately outside OSCORE protection.
      • If a message decrypts but is stale, inspect the Partial IV and replay window before blaming the proxy.
      • If privacy requirements include URI path or payload secrecy through a proxy, prefer OSCORE over hop-by-hop-only transport security.
      • If setup latency matters, consider whether the EDHOC-over-CoAP optimization can combine setup with the first protected transaction.
      Concept Map
      • EDHOC message_1 and message_2: exchange ephemeral public keys and negotiation data.
      • EDHOC message_3: completes initiator authentication and lets both endpoints derive OSCORE security material.
      • OSCORE request: uses Sender ID, sequence number, AEAD nonce, and protected plaintext fields.
      • OSCORE response: is processed with the matching recipient context and replay checks.
      Technical Accuracy Notes
      • This animation is a teaching model. It shows message order and protection boundaries, not exact byte-level COSE serialization.
      • OSCORE protects CoAP code, payload, and selected options as inner fields. Some outer fields stay available so proxies can forward messages.
      • EDHOC establishes keying material for OSCORE; deployments still need credential provisioning, authorization policy, and secure sequence-number persistence.
      • Replay windows help reject duplicate protected messages, but window size is an implementation and deployment tradeoff.
      Source Links