Participant Relationship Protocol

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C03-RI: Yes

Rationale

RFC 6550 sections 3.2.3 and 10.1 explicitly allow unsecured-mode RPL to rely on link-layer security. The previously unspecified access-controlled link is now bound to encrypted IEEE 802.15.4 data frames, rather than authentication alone. Linux v6.12 defines ENC_MIC128 as level 7. Its llsec_key_alloc selects ccm(aes), and llsec_do_encrypt_auth separates the MAC header as associated data from the payload passed to crypto_aead_encrypt when the ENC bit is set. The TX path invokes this function before transmission. Thus the 6LoWPAN dispatch/compression/fragment fields and the carried IPv6, ICMPv6 and RPL control fields are inside the encrypted MAC payload. This includes established DIS/DIO/DAO/DAO-ACK traffic when carried in the configured protected data frames. The positive finding uses the same visible-outer-framing allowance as C03-MQ/LP.

Assessment method

Explicit configuration selection and clear/encrypted field mapping; no runtime execution

Source context

RFC 6550 and Linux v6.12 link-security source, reviewed 2026-10-22

Outstanding qualification

This is a documentary mechanism/configuration witness, not a complete Linux RPL/DTLS executable qualification or radio capture. All relevant adjacencies and multicast transmissions must use the selected encryption policy; access control, MIC-only levels 1-3, or a mix of protected data with plaintext RPL controls does not satisfy it. Frame-control fields, MAC addresses, auxiliary security headers, frame counters/key selectors, sizes and timing remain observable. MAC acknowledgements and other link-management frames are not claimed hidden; the inspected Linux path even marks control-frame security support as incomplete. A locally captured pre-encryption TX packet is not proof of plaintext over the air. Link-key holders and forwarding routers can read RPL and IP routing information. No active-probe defense, endpoint-location anonymity, PQ protection, unprivileged operation, or traffic-analysis resistance is inferred. Keys and frame-counter lifecycle require correct provisioning. C02/F14, C04, D01 and the complete-stack execution evidence are unchanged; this is not an assertion that RPL unsecured mode encrypts itself.

Public sources

Editorial evidence references

The following identifiers refer to research records not included in this public package; they are not public links.