Contains KEYLEGIT bits.
KEYLEGIT bits - validity bits for this key.
Set if we believe the preceding key is legitimately owned by who it appears to belong to, specified by the preceding user ID. Computed from various signature trust packets that follow. Also, always fully set if BuckStop is set.
To define the KeyLegit byte does not require that OwnerTrust be nonzero, but OwnerTrust nonzero does require that KeyLegit be fully set to maximum trust.
This requires either: