Free tool · Download
Turn a message into five-figure groups that only someone holding the same pad can read. Ready Cipher, our free one-time pad tool, does the encrypt and decrypt math and shows every step on a paper-style worksheet, so you learn the method as you use it.
It is one HTML file. There is nothing to install and no account. It opens in Chrome, Edge or Firefox, it works offline, and nothing you type is saved or sent anywhere: close the page and it is gone.
Get Ready Cipher
The zip has the tool, a README and the one-page guide.
Open it in your browser · One-page guide (PDF) · Step-by-step instructions
On this page
How-To Video
Under two minutes: load a training pad, encrypt a message, read the worksheet, send the groups, decrypt them, and spot a miscopied group. Captions are burned in, so it works with the sound off.
Prefer to read? See the step-by-step instructions.
What It Does
- Encrypt: type the message and paste your pad. The worksheet shows the PLAIN, PAD and SEND rows exactly as you would write them on paper, and the green box holds the groups to send, key indicator first.
- Decrypt: paste the groups and the same pad. Ready Cipher checks the key indicator against your pad and marks any group that was miscopied.
- Print or copy: copy the groups, or print a message sheet to hand to a courier. For an ARRL or ARL Radiogram, ICS-213 or MARS form, paste the groups into the free Ready Messenger.
- Training pads: practise with the AmRRON TREE series, or make a printable practice sheet marked FOR TRAINING ONLY.
- The checkerboard: a printable reference for how letters become numbers.
- Works with Ready Ledger: the same checkerboard and pad math, so a message made in one reads in the other.
About the Pads
Ready Cipher does the math. It does not make your pads. A one-time pad is only unbreakable when the pad is truly random, when only you and the receiver hold copies, and when each pad is used once and then destroyed. A computer you browse the web on is not the place to make real pads, so the pads you use for real traffic should be made and kept under your own control, for example with ten-sided dice.
The training pads are for learning. The TREE series is public, and a practice sheet is made in your browser, so neither protects anything.
Know the radio rules
FCC rules for amateur radio (Part 97) and for GMRS and FRS (Part 95) do not allow messages encoded to hide their meaning, apart from narrow exceptions. A one-time pad message is for paper, a courier, or a service that allows it. Check the rules where you are before you send anything.
Want More? Ready Ledger
Ready Cipher is the one-time pad tool from Ready Ledger, our offline preparedness record, with the brevity codes left out. In Ready Ledger the same tool sits inside a full communications plan.
| Feature | Ready Cipher (free) | Ready Ledger |
|---|---|---|
| One-time pad encrypt and decrypt, worksheet, key indicator check | Yes | Yes |
| TREE series and practice pad sheets | Yes | Yes, saved with a destroy-by date |
| Brevity codebook: common words sent as one five-digit code, so messages are shorter and use fewer pad digits | No | Yes |
| Encrypted messages kept in an incident message log | No | Yes |
| DRYAD authentication sheets, codewords and duress word, channel code matrix | No | Yes |
| Your whole plan: people, places, radios, supplies, documents | No | Yes |
See Ready Ledger
One file, works offline, everything in one place.
Remember, Fortune Favors the Prepared
Semper Paratus, Semper Gumby