Appendix E: Reserved numbers

We reserve these certificate type values for Ed25519 certificates:

      [08] short-term descriptor signing key, signed with blinded
           public key. (Section 2.4)
      [09] intro point authentication key, cross-certifying the descriptor
           signing key. (Section 2.5)
      [0B] ed25519 key derived from the curve25519 intro point encryption key,
           cross-certifying the descriptor signing key. (Section 2.5)

      Note: The value "0A" is skipped because it's reserved for the onion key
            cross-certifying ntor identity key from proposal 228.