@ganyo https://developers.yubico.com/PGP/YubiKey_5.2.3_Enhancements_to_OpenPGP_3.4.html あたりを理解すると何かわかるのかも…
> Attestation is supported for all combinations of attestation key and attested key, except the attestation key cannot be from the curve25519 family. A fourth key slot is reserved for an attestation key. If specifying it by ID, it is Key ID 0x81. The Attestation template certificate is stored on a fourth user certificate slot reserved for it. It is selected directly with SELECT_DATA index 4. It can also be retrieved by calling GET_NEXT_DATA three times after SELECT_DATA on index 1
developers.yubico.comYubiKey 5.2.3 Enhancements to OpenPGP 3.4