Bip39 Library. From this position ahead the seed may very well be created on paper or spoken around telephone which opened up new, physical means of backing up the seed (multiple paper copies in several places, long lasting copies on metal plates with further protection from hearth/flood etc.). A standard https://finnqblvf.mywikiparty.com/1112098/the_anatomy_of_the_bip39_phrase_entropy_text_and_protection