{"algorithm":"Ed25519","publicKeyHex":"0e1b40472f388090c765bfeb6c67b9eedbfeba7cfb194fdf47f5b2dc333251e6","purpose":"x402 Content-Provenance C2PA MCP signing only (separate from the receive wallet's EVM key)","note":"Read back a signed C2PA attestation FREE at GET /v1/data/c2pa/attestation/{attestation_id}"}