localAttestationExtensionJson

Reads the attestation certificate chain the Android Keystore generated for alias and renders the leaf's key-attestation extension. The chain is produced when the key is created with an attestation challenge (as supreme-client does), so it is available right after an attestation run.

Renders the Android key-attestation extension of the locally created keystore key alias as human-readable JSON, or null if unavailable (iOS has no equivalent; the key may lack an attestation; or nothing is stored under alias).

iOS uses App Attest (no Android key-attestation extension); the iOS target is build-only here.