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Yet another card cipher idea
Topic Started: Jan 14 2014, 06:57 AM (197 Views)
Linokai
Member
[ *  * ]
This is kind of a continuation from my half deck cipher idea HERE.

Okay, so you split a deck of cards into two halves, each pile containing a black suit and a red suit.
The letter values of the cards are: red A-K = A-M respectively & black A-K = N-Z respectively.

For lack of more imaginative terminology, we'll call them deck 1 & deck 2.
For the example, both decks start unscrambled:

D1: ABCDEFGHIJKLMNOPQRSTUVWXYZ
D2: ABCDEFGHIJKLMNOPQRSTUVWXYZ

Plaintext is: SECRET.

The first letter will be encrypted with deck 1.

1) Since S is the 19th letter of the alphabet, go to the 19th card down.
obviously since they're unscrambled, the first CT character will be S.

2) Move all the cards above S to the bottom of the deck so S is now on top of the deck:

D1: STUVWXYZABCDEFGHIJKLMNOPQR

Next is the shuffle phase:

3) First move the top card (S) to the bottom of the deck:

D1: TUVWXYZABCDEFGHIJKLMNOPQRS

4) Take note of the face value of the next card, (Ace=1, Jack=11,Queen=12,& King=13).
Take that many cards off of the top, reverse their order and put them on the bottom of the deck.
In the example, the next card down is T, which is on a 7 card, so the top 7 cards are reversed and moved to the bottom:

D1: ABCDEFGHIJKLMNOPQRSZYXWVUT

5) Take note of the top and bottom cards of the deck (A & T)
Now, in Deck 2, do a triple cut with those two cards, like the jokers in the Solitaire Cipher.
(in the example, since A is the top card, just do a single cut and move all the cards below T to the top.)
after this phase the decks should look like:

D1: ABCDEFGHIJKLMNOPQRSZYXWVUT
D2: UVWXYZABCDEFGHIJKLMNOPQRST

The Next letter is encrypted with deck 2. The next letter is E, so go to the 5th card down, and put the first 4 cards on the bottom:

D2: YZABCDEFGHIJKLMNOPQRSTUVWX

The next CT letter is Y.

Next, move Y to the bottom:

D2: ZABCDEFGHIJKLMNOPQRSTUVWXY

Z is a King, so take the top 13 cards, reverse them and move them to the bottom:

D2: MNOPQRSTUVWXYLKJIHGFEDCBAZ

The top and bottom cards are M and Z, so now do a triple cut in deck 1 with M and Z. After this step, the decks should look like:

D1: YXWVUTMNOPQRSZABCDEFGHIJKL
D2: MNOPQRSTUVWXYLKJIHGFEDCBAZ

Then the next letter is encrypted with Deck 1, and so on and so forth...

(If the two designated cards for the triple cut are the top 2 cards, they just get moved to the bottom, and visa versa: If they're the bottom 2 cards, they get moved to the top.
If the top and bottom cards happen to be the same 2 cards for both decks, then the other deck doesn't get changed that round...)

So basically, you just alternate between deck halves each character and use them to shuffle each other.
Comments? Ideas for improvements? Criticisms? Insults? ;)
Edited by Linokai, Jan 14 2014, 07:08 AM.
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