One Time Pad Coding Tool

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$8.95 + tax & shipping

We looked at the methods promoted online for using One Time Pad encryption, but for the average Joe, it’s way too complicated. Most people have problems balancing their checkbooks, even more so performing modulo arithmetic!

So we created our One Time Pad Coding Tool that helps you produce either alphanumeric (letters and numbers) or numeric (numbers only) cipher text. You might want to use alphanumeric mode if you are speaking the cipher text, or numeric mode if sending it digitally. Both are easy to use.

To make your pad of random numbers, use our generator here.

Alphanumeric Encryption

Encrypting messages as alphanumeric cipher text is easy. On the tool, plain text is green, and the cipher text is red. As an example, let’s say that the next page of your pad reads

    8, 11, 42, 13, 39, 34, 6, 25, 23, 46, 19, 43, 36, 35

To encode the sample message “BACK SOON”:

    1. Select the next number from your pad (8, from the pad above).
    2. Find the number (8) in the PAD window.
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    3. Find the next plain text letter of the message, ‘B’, on the green ring.
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    4. Read off the red cipher text letter beside it, in this case ‘:’.
    5. Repeat from step 1 to encrypt the other letters of the message. (sp=space)
    Plain text B A C K sp S O O N
    Pad Number 8 11 42 13 39 34 6 25 23
    Cipher text : $ K ) B 8 I $ sp

    (You don’t have to write all this stuff down! Using the coding tool eliminates all this bookkeeping. Just record or send the cipher text as it is created.)

Alphanumeric Decryption

To decrypt the alphanumeric message, work backwards:

    1. Select the next number from your pad (8, from the pad above).
    2. Find the number (8) in the PAD window.
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    3. Find the cipher text letter on the red ring (‘:’).
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    4. Read off the green plain text letter, ‘B’.
    5. Repeat from step 1 to decrypt the other letters of the message.

Numeric Encryption

Encrypting messages as numeric-only cipher text is also easy, but requires a couple more steps. As with the previous example:

    1. Spin until the NUMERIC window is pointing to the green plain text letter, ‘B’.
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    2. Remember the plain text number in the window, in this case 70.
    3. Encrypt each digit of the plain text number using alphanumeric encryption to produce one or two numbers for your message. Use only the one’s digit from the pad, and throw away the ten’s digit.
    Plain text B A C K sp S O O N
    Numeric encode 70 1 71 77 90 82 5 5 4
    Pad Number
    (using only the one’s digit, underlined)
    8, 11 42 13, 39 34, 6 25, 23 46, 19 43 36 35
    Cipher text 99 9 42 31 47 23 2 9 9

    (You don’t have to write all this stuff down! Using the coding tool eliminates all this bookkeeping. Just record or send the cipher text as it is created.)

Numeric Decryption

To decrypt the message, work backwards:

    1. Use the alphanumeric decryption steps above for each digit in the message. Use only the one’s digits from the pad.
    2. For each one or two decrypted digits, find them in the NUMERIC window and read off the green plain text character.
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Notice that the letters A, E, I, N, O and R have single digit numeric encodings (1 through 6), whereas all the others have two digit encodings, so you’ll have to be careful of that. Also observe that the numeric method uses up your pad quicker.

With a little practice, you should be able to encrypt and decrypt messages without writing down intermediate information. Our tool makes numeric one time pad encoding much easier than computing with pencil and paper.

Security

As you use each section of your pad, tear it off and destroy it. It’s easiest to use each page from the bottom up, tearing off each used section immediately after use. Do not ever reuse a pad section.

padTo help the receiving person know what section of the pad you are using, transmit the first two numbers from the pad section to indicate which part of the pad you are using. Transmit these in the clear as they are just random numbers having no meaning to anyone without the pad. Then use pad numbers after the first two you transmitted.

You can even assign different pads to different people or groups, as your organizational needs demand.

Authentication

Encryption is good, but what if someone captures your pad and sends bogus messages to your friends? They would have no way to know it’s not you sending the messages. To avoid this problem, be sure you sign your messages with an authentication code of your choosing. There are several ways to do this:

  • Give each person has his or her own code
  • Use one code for the entire group
  • Use a code that changes with each message, like the time of day or a message number

If no one ever writes down the authentication code, then people capturing your written communiques would have no idea it was even needed, and the messages they sent would be ignored, and would be a warning that something was wrong.

A sample plain text message might be, “MEETING AT 18:00 HRS. BR549”. (The text “BR549” is the authentication code.)

Purchase the Coding Tool

The One Time Pad Coding Tool is available for purchase now. It is made in the USA, water resistant, four inches square, and will fit in your pocket or pack for field use. Instructions for encryption and decryption are on the back, as well as on this page. Get one for each member of your team. The only additional thing you need is the pad of numbers, which you can generate here for free!

Purchase the coding tool for $8.95 plus tax and shipping through our Paypal cart. This product is available in the US and Canada only.