The One-Time Pad is old-school tradecraft and remains the one truly unbreakable system for passing messages between allies - assuming both parties maintain proper OpSec.

Definition of One-time pad. One-time pad (OTP), also called Vernam-cipher or the perfect cipher, is a crypto algorithm where plaintext is combined with a random key. It is the only existing mathematically unbreakable encryption.

To use an OTP, you first have to convert your plaintext to a simple numeric code such as this:

A=11 B=12 C=13 D=14 E=15 F=16
G=27 H=28 I=29 J=30 K=31 L=32
M=43 N=44 O=45 P=46 Q=47 R=48
S=59 T=60 U=61 V=62 W=63 X=64
Y=75 Z=76 0=77 1=78 2=79 3=80
4=91 5=92 6=93 7=94 8=95 9=96

Roll five (5) 10-sided dice (d10) to generate a unique and random identifier:

(in our example the random identifier is 98634)

Roll five (5) 10-sided dice (d10) to generate a set of random number groups of five (5) digits each:

98634 78493 09873 20563 24384
48243 18343 02539 12043 10345
10509 06782 12345 10367 10235
10324 03867 73825 46813 97616
54321 93265 12309 73654 73544

You will have two copies of a OTP. One for the sender and one for the receiver.

Let’s now take the message “USE PLAN ALPHA7” and encode it.

1. USE PLAN ALPHA7

2. 61-59-15-46-32-11-44-11-32-46-28-11-94

3. Now take the numbers from your OTP

4. 98-63-47-84-93-09-87-32-05-63-24-38-44

5. And add the two. If the answer is greater than 100, then subtract 100.

6. 61-59-15-46-32-11-44-11-32-46-28-11-94
+98-63-47-84-93-09-87-32-05-63-24-38-44
=59-22-62-30-25-20-31-43-37-09-52-49-38 → This is your ciphertext.

7. To decode, take your ciphertext and subtract the numbers from your OTP to get the numeric code. If the answer is a negative number, add 100.

8. 59-22-62-30-25-20-31-43-37-09-52-49-38
– 98-63-47-84-93-09-87-32-05-63-24-38-44
= 61-59-15-46-32-11-44-11-32-46-28-11-94

9. Finally, convert the numeric code to plaintext
.
10. 61-59-15-46-32-11-44-11-32-46-28-11-94

U-S-E-P-L-A-N-A-L-P-H-A-7

Note: Remember to designate the first set of five (5) digits on the OTP as your identifier.  This identifier is NOT included in your encrypted message - it is merely used to ensure you begin deciphering your message from the proper place.

Buy your One-Time Pad Kit! Kit includes: Two (2) packs of Five (5) d10 dice 25 sheets of III Carbonless Paper OTP Fundamentals 101 Instructions $14 + S&H In Stock - Ships within 24 hours!