Bip39 Wiki. Theoretically, you can Assume out the mnemonic phrase by his possess, but It's not at all Protected, because a human cannot do an incredible work with the random technology. The ultimate way to protected a single’s wallet is to take a mnemonic phrase created by the program code. https://reallivesocial.com/story4080535/bip39-adalah-bip32-vs-bip39-no-further-a-mystery