Bip39 standard https://send.now/zchzg5fu4oku Checksum development: A checksum is produced from this entropy applying SHA-256 hashing, which assists confirm the mnemonic's integrity later. For words that have only 3 letters, there isn't a 4th letter. One example is Using the word “insert”, there won't be any more letters afterwards and therefore https://health-lists.com/story20566560/bip39-words-bip39-checksum-an-overview-https-cutt-ly-uryc5rw7