Bip32 and bip39 https://www.plurk.com/p/3hf2syltjx Even though it uses BIP32 approach you'll be able to continue to import BIP39 seeds into Electrum wallet. Also other than BIp32 There is certainly BIP44 version which some wallet use to the generation of seeds. The amount safety does a passphrase incorporate? A BIP39 passphrase https://trackbookmark.com/story22128897/bip39-checker-bip39-compatible-wallet-can-be-fun-for-anyone-https-cutt-ly-uryc5rw7