BIP32_
Offset for hardened child key derivation (2^31).
Per BIP-32: "Hardened child keys are derived using indices i >= 2^31 (i.e., the leftmost bit is set). Normal child keys use indices i < 2^31."
SLIP-0010 requires hardened derivation for Ed25519 keys because Ed25519 does not support non-hardened derivation.
SEP-5 uses the path m/44'/148'/n' where all components are hardened.