Bip39n Code. From this point ahead the seed may very well be written on paper or spoken above telephone and this opened up new, physical means of backing up the seed (several paper copies in various spots, sturdy copies on metallic plates with added defense from hearth/flood and so on.). https://financepublique26047.wikilowdown.com/6499260/the_anatomy_of_a_bip39_phrase_entropy_phrases_and_security