Proof of Process (PoP): Architecture, Evidence Format, and VDF

Introduction The rapid proliferation of generative artificial intelligence has created an authenticity crisis in digital discourse. While traditional provenance tracks the "custody of pixels," it fails to attest to the human-driven process of creation. This document specifies the Proof of Process (PoP) protocol, which extends the RATS architecture [RFC9334] to validate the "provenance of effort."

Core Principles The PoP framework is built upon five foundational pillars:

Physics-based Cost: Using memory-hard sequential functions (Argon2id) to establish an economic lower bound on forgery.
Physical Freshness: Anchoring sessions to non-deterministic physical markers (e.g., thermal noise) to prevent replay.
Biological Binding: Entangling human motor-signal jitter as a non-deterministic seed for cryptographic proofs generated within the Attesting Environment (AE).
Out-of-Band Presence: Utilizing secondary physical devices (e.g., smartphone QR scans) to bridge the digital-physical gap.
Asymmetric Verification: Ensuring that complex, long-duration proofs can be verified efficiently by third parties.

RATS Role Mapping

Attester:: The writing environment (e.g., a text editor or OS service) that captures behavioral events and generates PoP Evidence packets (.pop).
Verifier:: A trusted entity that appraises PoP Evidence and issues a Writers Authenticity Report (WAR).
Relying Party:: An end-user or system that consumes the WAR to make a trust decision.

Attester State Machine To ensure protocol robustness, the Attesting Environment (AE) MUST implement a formal state machine:

RECORDING: AE captures semantic events and physical telemetry into a hash-linked buffer.
PENDING_CHECK: The event block is frozen to initiate a VDF proof.
CHECKPOINT: AE computes the VDF and weaves the entangled seed into the chain.
SEALING: The final transcript root is signed by the hardware Secure Element.

Evidence Content Tiers and Assurance Levels PoP Evidence is classified by both content depth (CORE, ENHANCED, MAXIMUM) and attestation assurance strength (T1-T4):

Tier	Binding Strength	NIST AAL	EAT Level
T1	Software-only	AAL1	0-1
T2	Opportunistic hardware	AAL1-2	1-2
T3	Required TPM/Enclave	AAL3	3
T4	Discrete TPM + PUF	AAL3+	3+

Evidence Format and CDDL Evidence Packets are identified by the semantic CBOR tag 1347571280. uint, ; version 2 => tstr, ; profile-uri 3 => uuid, ; packet-id 4 => pop-timestamp, ; created 5 => document-ref, ; document 6 => [+ checkpoint], ; checkpoints ? 7 => attestation-tier, ; T1-T4 assurance level ? 8 => [* tstr], ; attestation-limitations ? 10 => [+ presence-challenge], ; QR/OOB presence proofs ? 18 => physical-liveness-section, ; CDCE markers } checkpoint = { 1 => uint, ; sequence (strictly monotonic) 2 => uuid, ; checkpoint-id 4 => hash-value, ; content-hash 9 => process-proof, ; process-proof (VDF) 10 => jitter-binding, ; behavioral-entropy 11 => physical-state, ; Thermal/Entropy Weave 12 => bstr .size 32, ; entangled-mac (HMAC-SHA256) } document-ref = { 1 => hash-value, ; content-hash 3 => uint, ; byte-length ? 5 => hash-salt-mode, ; 0=unsalted, 1=author-salted ? 6 => bstr, ; salt-commitment } ]]>

VDF and Temporal Proofs Implementations MUST support Argon2id [RFC9106] as the MTI memory-hard function.

Hardware-Anchored Time (HAT) In T3/T4 tiers, the AE MUST anchor the VDF seed to a TPM Monotonic Counter.

Non-deterministic Physical Freshness To prevent replay, the VDF seed MUST incorporate physical markers (thermal noise/kernel entropy) sampled within the AE at the start of the session.

IANA Considerations This document requests registration of CBOR tags 1347571280 ("PPP ") and 1463894560 ("WAR "), and the EAT profile urn:ietf:params:rats:eat:profile:pop:1.0.

Security Considerations The primary security goal is to provide tamper-evident records of document evolution. Implementations MUST validate all CDDL constraints and ensure checkpoint sequence monotonicity.