Bip39 Seed To Private Key. From this point forward the seed might be created on paper or spoken about telephone which opened up new, physical ways of backing up the seed (various paper copies in numerous spots, strong copies on metallic plates with added defense from fire/flood and so on.). https://financedepartment73827.wikinstructions.com/1111524/the_anatomy_of_the_bip39_phrase_entropy_text_and_protection