Bip39 seed phrases https://penzu.com/p/2ea6922b70254307 Checksum generation: A checksum is generated from this entropy working with SHA-256 hashing, which assists confirm the mnemonic's integrity later. For words that only have 3 letters, there is no 4th letter. By way of example with the word “add”, there aren't any additional letters afterwards https://bookmarkpressure.com/story20073430/bip39-deutsch-an-unbiased-view-of-bip39-2048-words-https-x-com-tundra838554