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." Unlike traditional attestation which captures static system state, PoP attests to a continuous physical process. It introduces Proof of Biological Space-Time (PoBST) to enforce temporal monotonicity and Cross-Domain Constraint Entanglement (CDCE) to bind behavioral entropy (human jitter) and physical state (thermodynamics) to the document's evolution.

Terminology

Attester:: The combination of an Attesting Environment (AE) and Target Environment (TE) responsible for generating PoP Evidence.
Checkpoint:: A cryptographic commitment to a block of events and the document state, bound by a VDF.
PoBST:: Proof of Biological Space-Time. A memory-hard sequential function with asymmetric verification, entangled with human jitter.
CDCE:: Cross-Domain Constraint Entanglement. The method of weaving jitter and thermodynamics into the cryptographic chain.

Core Principles PoP operates on five primary constraints:

Physics-based Cost: Memory-Hard Sequential Functions (MHSF) establish an economic lower bound on forgery.
Physical Freshness: Replay and simulation attacks are defeated by anchoring sessions to non-deterministic physical markers (thermal noise).
Biological Binding: Captured human motor-signal randomness (jitter) serves as the non-deterministic seed for the spacetime proof.
Out-of-Band Presence: Utilizing secondary physical devices (e.g., smartphone QR scans) to bridge the digital-physical gap.
Asymmetric Verification: PoBST allows complex 10-hour proofs to be verified in milliseconds.

Attester State Machine The AE MUST implement the following formal state machine:

RECORDING: AE captures semantic events and physical telemetry into a hash-linked buffer.
PENDING_CHECK: The current event block is frozen to prepare for a checkpoint.
CHECKPOINT: AE computes the VDF over the block hash and incorporates the entangled seed.
SEALING: The Attester generates a final snapshot, signs the transcript root with a hardware Secure Element, and prepares the transport container.

Attestation Assurance Levels Attestation Assurance Levels (T1-T4) define the strength of hardware binding, mapping to NIST SP 800-63B Authenticator Assurance Levels (AAL) and EAT security levels [RFC9711].

T1: Software-Only: Baseline evidence generation without hardware anchors. Equivalent to AAL1.
T2: Attested Software: AE attempts to use platform security APIs (e.g., keychain integration) but degrades gracefully. AAL1-2 equivalent.
T3: Hardware-Bound: Requires TPM 2.0 or platform Secure Enclave key binding. Evidence generation MUST fail if hardware is unavailable. AAL3 equivalent.
T4: Hardware-Hardened: Maximum assurance with discrete TPM, PUF binding, and enclave execution for timing-sensitive operations. AAL3+ equivalent.

Evidence Format and CDDL Evidence Packets are CBOR-encoded and identified by semantic 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 ? 10 => [+ presence-challenge], ; QR/OOB proofs ? 18 => physical-liveness-section, ; CDCE markers } checkpoint = { 1 => uint, ; sequence (strictly monotonic) 2 => uuid, ; checkpoint-id 3 => pop-timestamp, ; timestamp (local) 4 => hash-value, ; content-hash 5 => uint, ; char-count 6 => edit-delta, ; delta 7 => hash-value, ; prev-hash 8 => hash-value, ; checkpoint-hash 9 => process-proof, ; VDF (PoBST) 10 => jitter-binding, ; behavioral-entropy 11 => physical-state, ; CDCE Weave 12 => bstr .size 32, ; entangled-mac (HMAC-SHA256) } document-ref = { 1 => hash-value, ; content-hash 3 => uint, ; byte-length 4 => uint, ; char-count ? 5 => hash-salt-mode, ; 0=unsalted, 1=author-salted ? 6 => bstr, ; salt-commitment } edit-delta = { 1 => int, ; chars-added 2 => int, ; chars-deleted 3 => uint, ; edit-operations-count } physical-state = { 1 => [+ float16], ; thermal-trajectory-delta 2 => uint, ; entropy-pool-delta } ]]>

VDF and Temporal Proofs

Memory-Hard Sequential Functions (Argon2id) Implementations MUST support Argon2id [RFC9106] as the MTI memory-hard function. Default parameters: Time Cost (t)=1, Memory Cost (m)=2^16 (64 MiB), Parallelism (p)=1.

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

Non-deterministic Physical Freshness The VDF seed MUST incorporate Non-deterministic Physical Freshness derived from physical events (e.g., thermal noise) sampled within the AE at the start of the session to prevent replay attacks.

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 in their respective registries.

Security Considerations

Relay and Diversion Attacks Evidence packets are self-contained and bound to document content, making them independently verifiable. No session binding is required between Attester and Verifier, eliminating connection-based vulnerabilities.

Replay Attacks Defeated through Physical Freshness. Replaying a session requires replaying the immutable hardware physics of the AE at the exact microsecond of the original capture.