How Bitcheque
works

This is an experimental research project: nothing on it is a promise of value. Your key is a cheque book printed from one seed. To transfer, you copy or scan a few boxes from a cheque and hand them to any computer. The chain only checks hashes; once the book is printed, no device holds or signs with your key.

One cheque,
one line of digits.

A cheque says one thing: transfer this amount to this account. It is written as 18 digits, one column per digit and one row per value 0 to 9.

1
Recipient · 12 digits
11-digit account number plus a check digit. One wrong digit and the chain rejects it instead of sending to a stranger.
2
Amount · 6 digits
Four significant digits, an exponent and a fee tier. 1.5 coins is written 1500 × 10^5.
3
Each box is a secret
Every box holds 12 printed words. The box each digit points to is the one you copy.

Example: transfer 1.5 coins, fee tier 200000048213-5 · 1500 5 2

The 18 orange boxes are the ones you copy. Every other box stays on paper, forever.

Make your book, once.

About 20 minutes on one clean, offline computer. About two hours after registering, your account number is final.

Go offline

A freshly booted clean computer, every network off, printers on USB cables only.

Write down your seed

24 words, on paper. It is the only backup of the whole book.

Print in two parts

Part A holds the recipient columns, part B the amount columns. Print them separately, ideally on two printers, store them apart, then switch everything off.

Register and check

Open the registration file, which holds only public hashes, on any online computer: a minute or two of proof of work registers the book. Cheque 0, for zero coins, proves the book is honest. About two hours later, scan the code on your sheet to see your account number.

Make one step by steparrow_forward See a sample book

Transfer: copy, then send.

Bring the two parts together and take the next unused cheque.

Write recipient and amount

Get the 12-digit number from the recipient directly. The site or a printed table converts the amount.

Find the 18 boxes

In each column, find the row for that digit: 12 boxes in part A, 6 in part B.

Copy or scan the boxes

Type each box's 12 words, or scan its QR code with the cutting template so only that box shows.

Broadcast from anywhere

Verify, then broadcast. Then destroy the rest of that cheque.

Write a cheque nowarrow_forward

Why it's safe.

No device signs

Signing is copying. The computer that broadcasts only gets the boxes for this one transfer, and cannot change the recipient or the amount.

Hashes only

The chain stores one SHA-256 hash per box and compares. No elliptic curves, so a quantum computer has no shortcut.

The chain remembers

The chain records which cheque numbers are used, so none can be reused. You keep only the seed and the paper.

What to keep,
and the limits.

Item	Where
Seed · 24 words	Place 3, away from the book
Part A · recipient	Place 1
Part B · amount	Place 2
Anything else	Nothing: no files, counters or app state

swap_horiz
An unused cheque can move coinsAnyone holding both parts of an unused cheque can make one move.
counter_9
Ten moves per bookWhen they run out, cheque 11 sweeps everything to a new book.
key_off
Don't lose seed and book togetherA lost book can be reprinted from the seed; losing both loses the account.
lock
A safe, not a walletBuilt for holdings that move rarely, not for frequent transfers.

Read the full specification FAQ

How Bitchequeworks

One cheque,one line of digits.