Book Cipher × Bitcoin
How the Book Cipher
protects your seed phrase
Offline, physical, and simple.
Two pieces that are worthless apart.
What is a Book Cipher?
A method used by spies and diplomats for centuries — now applied to Bitcoin seed backup.
The Book Cipher is one of the oldest encryption methods in existence. The idea is simple: instead of writing a secret word, you write a reference to where that word appears in a specific book. The message looks like a list of meaningless numbers — unless you have the exact same book.
Spies and diplomats used this method for centuries precisely because the numbers raise no suspicion. A list of numbers could be anything: an inventory, a phone log, a receipt. Without the key book, they are nothing.
How It Works with BIP39
BIP39 seed phrases consist of 12 or 24 words from a fixed list of 2,048 words. BIP39 Books contain all of them.
Get a BIP39 Book
Your book contains all 2,048 BIP39 seed words, woven naturally into its text. It looks and reads like a regular book.
Find Each Seed Word
Look up every word of your seed phrase in the book. Use the downloadable word index to find them quickly by page number.
Note the Position
For each word, write down its page, line, and word number. That three-part reference is your encoded seed word.
Repeat for All Words
Do this for all 12 or 24 seed words. The result is a compact list of number triplets — your complete backup.
Store Separately
Keep the book in one place and your number list somewhere else. Together they reconstruct your seed. Apart, they reveal nothing.
Test Your Backup
Use the numbers and the book to decode your seed phrase and verify it matches. Do this before you rely on it.
Worked Example
Your first seed word is "abandon". You find it in the book on page 12, line 5, third word on that line. You write:
1. 12-5-3
Repeat for seed words 2 through 24. The result is a numbered list of 24 triplets — compact, innocent-looking, and completely meaningless without the exact book.
Why Two Pieces?
Security through separation. Neither piece is useful on its own.
Book Alone
Just a book on a shelf — or in your backpack. No indication of which wallet, which seed, or even that Bitcoin is involved. Anyone who finds it sees a children's story or a collection of wisdoms.
Numbers Alone
A list of number triplets with no context. They could be coordinates, phone extensions, product codes — anything. Without the exact book, they cannot be decoded.
Book + Numbers
Your complete seed phrase, reconstructed in minutes. This is the only combination that matters — and you control where each piece lives.
Creative Ways to Store Your Numbers
The number list is short and flexible. It can be disguised as almost anything ordinary.
Your encoded seed is just a list of numbers. That gives you enormous flexibility in how you store it — or hide it in plain sight. The goal is something that raises zero suspicion even if found by the wrong person.
Phone Contact List
Split the numbers across several fake contacts. "Aunt Martha" has a phone number that is actually your first six seed positions.
GPS Coordinates
Format your numbers to look like geographic coordinates. A list of "locations" in a notes app or travel journal.
Dates and Scores
Write them as dates, times, sports scores, or reference numbers in a notebook. Completely ordinary in any context.
Measurements or Codes
Format as serial numbers, product codes, dimensions, or any other numeric sequence that fits naturally into your life.
Combine with physical durability
Simple paper works for most people. For additional resilience against fire or water, consider engraving or stamping your numbers onto a metal plate. Metal plates are a complementary option — they protect the durability of your number list, while the Book Cipher protects its meaning.
The book itself is a standard printed paperback — multiple copies are easy to obtain, and having a spare on a second shelf in a different location is straightforward.
Security Best Practices
A few simple rules make the difference between a solid backup and a risky one.
Keep book and numbers in separate locations
This is the core security principle. If both pieces are in the same place, the backup offers no more security than writing your seed phrase on a piece of paper. Different rooms, different buildings, or different cities — the further apart, the better.
Have a backup copy of the book
Books can be lost, damaged, or go out of print. Keep a second copy of the book in a different location. Because BIP39 Books are real, published books available on Amazon, obtaining an additional copy is straightforward — but do it before you need it.
Test your backup before relying on it
After encoding your seed, decode it again using only your number list and the book. Verify it matches your original seed phrase word for word. A backup you have never tested is a backup you cannot trust.
Do not use this as your only backup
The Book Cipher method is an excellent complement to other backup approaches — not a replacement. Maintain at least two independent backup methods. If you lose access to one, the other keeps your Bitcoin safe.
Tell a trusted person about the system
A backup that only you understand is a problem if something happens to you. A trusted family member or friend should know that a BIP39 Book exists, where the book is, and that there is a corresponding number list — even if they do not know where the numbers are stored. This ensures your Bitcoin can be recovered by your heirs.
Ready to Start?
Choose your BIP39 Book
Both books contain all 2,048 BIP39 seed words and work exactly as described on this page. Choose the one that fits your shelf — or compare both as a bitcoin seed book on the homepage.
Compatible with any BIP39 wallet: Bitcoin, Ethereum, and dozens of other cryptocurrencies.
Veit the Fox
A children's adventure story. Perfect if you have kids at home — read it aloud while it quietly protects your Bitcoin.
Available NowLearn More →
777 Wisdoms
777 daily wisdoms for your nightstand, travel bag, or office shelf. A natural fit for any adult's bookshelf.
Available NowLearn More →
Not financial advice. Using any backup method is done at your own risk. Always maintain multiple backups and verify you can recover your seed phrase.