Bip39 Checksum. It’s a reminder of the critical relevance of securely storing your seed phrase and your passphrase. In the event you were being to expose your seed phrase underneath duress, your hidden wallets would remain protected and unknown. From in this article onward we don't use the hardened derivation. https://agendabookmarks.com/story19444969/bip39-mnemonic-https-linktr-ee-bip39-bip-39-no-further-a-mystery