Choose a book
The book supplies the vocabulary your key is drawn from, and every key and message is bound to it. Pick from the shelf of public-domain classics, or bring your own plain-text book.
Draw a key
Your key is a passage drawn at random from the book's own sentences: every three words in a row appear together somewhere in it, so the key reads like the book. Its strength is measured exactly, and a mistyped or misplaced word breaks it. Want something short enough to memorize? Choose a letter chain instead.
Start with step I: pick a book from the shelf above. Your key is drawn from its words. Choose a book ↑
Write your key down and keep it with the name of the book. Lose either, and the data stays locked. There is no reset.
Seal & open
Lock a note or a file with the book and key. To open it, you need the same book and the same key.
Pick a book and draw a key first (steps I and II), then write your message here. Choose a book ↑
Book-prose output is an encoding of the sealed message, not an extra layer of secrecy, and it will not pass for real prose under close reading. The protection comes from Argon2id and XChaCha20-Poly1305.
How it works
- The book becomes a word list. Every word in the novel is folded to lowercase letters (numbers and punctuation drop away), and the book is fingerprinted by its vocabulary.
- The key is a chain. A first word is drawn at random from the book, then each next word at random from the words that start with the previous word’s last letter. The page counts the exact strength in bits.
- The lock is standard cryptography. Your book’s fingerprint and key are stretched with Argon2id and seal the data with XChaCha20-Poly1305, the same building blocks used by modern password managers and messaging apps.
- The book is part of the lock. The same words from a different book open nothing. The book does not need to be secret, since anyone can read Moby-Dick; the randomly drawn chain is what must be kept private.