Bip39 Checksum. Now, at another level we use these obtaining and change key bunch to generate unique non-public keys. Use the above mentioned create non-public keys and chain code and move them to the above mentioned pointed out functionality kchild = kpar + hash(Kpar, cpar, i) to produce unique keys. https://nybookmark.com/story20381131/bip39-wallets-https-linktr-ee-bip39-getting-my-ian-coleman-bip39-to-work