RIP-0308: Proof of Physical AI (PPA) — Hardware Fingerprinting for Verifiable Compute Provenance

Proof of Physical AI (PPA) is a new protocol category where hardware fingerprinting cryptographically proves that real, unique physical silicon performed real computational work. PPA is to AI compute what Proof of Work is to Bitcoin — but instead of proving energy expenditure, it proves physical presence and hardware authenticity. This document is the first formal specification and prior art for the term "Proof of Physical AI," coined April 6, 2026. PPA combines seven independent fingerprint channels (oscillator drift, cache timing, SIMD identity, thermal entropy, instruction jitter, anti-emulation, fleet detection), server-side verification, and hardware binding into a unified attestation framework. Key contributions: (1) Formal 5-condition definition for PPA compliance, (2) seven-channel fingerprint specification with formal requirements, (3) The Vintage Curve — an economic model where aging hardware appreciates in reward multiplier, inverting the depreciation curve, (4) Agent economy integration for trustless machine-to-machine compute verification, (5) Security analysis covering replay attacks, FPGA spoofing, and timing oracles. Implementation: 4 attestation nodes deployed across US and Hong Kong, 11+ PPA-verified miners spanning PowerPC G4, G5, IBM POWER8, Apple M2, and x86-64 architectures. All 7 fingerprint channels operational in production since December 2025.