Function carried_key_well_formed 

pub fn carried_key_well_formed(key: &[u8], profile: Profile) -> bool

Whether key is a key in its one carried form for profile (D13): exactly 2,592 bytes in pq_pure, and in pq_hybrid the ML-DSA-87 key followed by a DER RSAPublicKey that encodes back to the same bytes, with a 4,096-bit modulus and exponent 65537. It says nothing about who holds the key.