Bip39 to binary https://ameblo.jp/generate-bip39brooks/entry-12913353546.html Regardless that it employs BIP32 technique you could even now import BIP39 seeds into Electrum wallet. Also other than BIp32 There is certainly BIP44 Edition which some wallet use for your technology of seeds. For words that only have three letters, there isn't any 4th letter. https://www.empowher.com/user/4550298