March 11, 2012

ANONTELPRO #4 - Cryptanalysis 101

ANONTELPRO #4 - Cryptanalysis 101

Good evening, AnonInts. Tonight you learn the Fibonacci Cipher, also known as a One-time-pad (OTP).

Fieldcraft #2 OTPz: The OTP method is pretty old, dating from 1917, but still in use today by all CGCI, and many well organized resistance groups. This is because it is simply unbreakable: If a message is intercepted, no biggie, CGCI don't have the key. If the key is intercepted, no biggie, CGCI don't know the proprietary values of your encryption.

Materials Required: You'll need paper, preferably graph paper of smallish rule. You'll need dice. I recommend 2, for simplicity's sake. I also recommend you use different colors of ink too, so you don't confuse yourself. So grab your blue black and green pens (nobody ever liked red) and let's get rolling, lol.

Protips: Don't make the key at your desk. If your house is bugged, cameras with fiber optic lenses can be placed anywhere with apertures the size of pinholes. Pick a private spot unlikely to have a camera trained on it. Never use the same key twice/never reuse blocks. Don't decrypt on your keypad, use a seperate working piece and shred or preferably burn or even eat it afterward. That's not a joke. #OperationalSecurity

Making Your Key:

Method 1: Roll, roll, roll. You want to roll the dice and record on your graph paper what you roll. (leaving at least one rule above and below, but I recommend 2 above and below so you don't confuse yourself later) If you roll a single digit, record it with a 0. For instance a 3 and a 4 record as 07. Don't fret if you roll doubles of the same or even triples. That makes it nicer.

Method 2: String random letters out, then use Schoolboy's Code (Described next section) to convert them to numbers. It's cool because it will still be random, perhaps random-er.
It'll look something like this:

Key 120306111107090203040404 etcadnauseam (or until you run out of paper)

*Protip: make your key as long as possible so you can use it a couple times, and don't say "key" on it.

Now break your key into blocks of numbers (to further baffle cryptanalysts, and to make it easier for you to manage.)

Key 120306 111107 090203 040404

Deciding Your Alphabet: For the example we will use Schoolboy's Code (A1-Z26) as the values of the alphabet. Operationally, it is not recommended that you do this. (Since that'll be the first thing CGCI will test if they intercept both your message and key.) Your group should pick its own 2 digit values for every letter, and encrypt/decrypt accordingly.

*Protip: Spell out all punctuation and numerals in longtext. Use an X as "." Use XX to end your message text, then add extra characters to finish key block.

Encrypting: Repeat the first block in your message as a placeholder, so the recipient knows where on the key to start decryption after. The OTP is encrypted by use of Fibonacci Addition. It's addition in which there is no carrying, eg: 9+2=1, not 11. 1+9=0, not 10.

Our message is going to be HI. LULZ. (080924 122112262424)

P is for Plaintext, K is for Key, E is for Encrypted Message.

I demonstrate:

P              080924 122112 262424
K  120306 111107 090203 040404
E  120306 191020 112315 202828

See'd wut I did thar? Questions tweet @LLCStr1ng3r

Decrypting: To decrypt you use Fibonacci Subtraction. If you get a negative number, you add 10 to the encrypted line. I'll underline instances to make it more obvious.

E  120306 191020 112315 202828
K  120306 111107 090203 040404
P  -NULL  080924 122112 262424

Now apply your alphabet values to P.

080924 122112 262424
H  I  X  L  U  L  Z X X

I hope you find this useful, or at the very least informative. As always feel free to tweet comments or questions, and if you want more Cryptanalysis posts, say so. There are many different types of ciphers and all are interesting, this is simply the only one that can never be broken without both the key and code and method. There are some ciphers that do not require keys, as they are moderately well known/elementary, and the key can be memorized. I personally don't consider these secure unless they are highly modified so as to be proprietary, so I did not deem them to be of interest to Anon.


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