Bip39 mnemonic checksum https://www.bitsdujour.com/profiles/wWbptt It's important the mnemonic sentences are produced from randomly selected figures! These numbers is often produced in many different different ways, which might be described in other articles below, like "Exactly what is an RNG" and Seed Phrase Generation. He is also the creator of essentially https://penzu.com/p/2ea6922b70254307