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ZK Proof Details

The SP1 program proves the following:

  1. The photo bytes matches the expected bytes in the C2PA manifest
  2. The Apple Attest attestation is valid
  3. The assertion (i.e. signature of the photo hash using the attested key) is valid

The photo bytes are provided as input to the proof.

Proof Logic

StepOperationGuarantees
1Extract manifest from photo bytes—
2Extract bindings and data hash from manifest—
3Compute photo hash—
4Check data hash == photo hashManifest corresponds to this photo
5Validate attestationThe attestation is valid and from Apple
6Validate assertionPhoto hash was signed by the attested key

Attestation Validation

Guarantees:

  • The device key was generated in a genuine Apple Secure Enclave
  • The key is bound to a specific app (via app_id / RP ID)
  • The device is running a legitimate app (AAGUID = appattest or appattestdevelop)

Validates:

  • Certificate chain verifies up to Apple Root CA
  • Nonce matches the challenge
  • Public key hash matches the key ID
  • RP ID == SHA256(app_id)
  • AAGUID is a valid Apple attestation identifier

Assertion Validation

Guarantees:

  • The photo corresponding to this hash was signed using the ZCAM SDK

Validates:

  • ECDSA signature over the photo hash using the public key from attestation

Public Outputs

  • Photo hash (SHA-256)
  • Apple Root CA certificate

These committed values allow verifiers to confirm the proof corresponds to a specific photo and chains to Apple's actual root certificate.