Fortunately, in 2012 the developer Pieter Wuille created the BIP32 specification at The bottom with the hierarchical deterministic wallets. Alongside one another with it, Pieter made a mathematical functionality to make a master essential from which to derive all other keys inside of a deterministic way. This information clarifies BIP39, http://edgargvkh682.theburnward.com/from-mnemonics-to-security-understanding-bip39-passphrases-and-their-importance-in-copyright