The batch size requirement is imposed by the FIDO spec, to ensure that batch IDs are not so high entropy as to pose a privacy problem. "In this Full Basic Atte

The batch size requirement is imposed by the FIDO spec, to ensure that batch IDs are not so high entropy as to pose a privacy problem. "In this Full Basic Attestation model, a large number of authenticators must share the same Attestation certificate and Attestation Private Key in order to provide non-linkability (see Protocol Core Design Considerations). Authenticators can only be identified on a production batch level or an AAID level by their Attestation Certificate, and not individually. A large number of authenticators sharing the same Attestation Certificate provides better privacy, but also makes the related private key a more attractive attack target."