>>221Not really a game, but something comfy that you can do with cards. It's called Solitaire (or sometimes Pontifex), and has nothing to do with the normal cardgame called Solitaire that is very popular among senior citizens.
You start off with a secret message that you want to encrypt. Conventionally, you separate it into 5-character segments. An example is DONOT USEPC for "Do not use PC". Keep the message short because you're encrypting it character-by-character by hand.
Another pre-requisite is that your Joker cards are different. One has to be "A" and one has to be "B". Usually one joker is in color and one joker is black&white. Make the black&white one the "B" Joker, because B is for Black. If they're both the same coloring, but one has a larger image on it (like a bigger star or more writing), then make that one the "A" Joker. It's important that we can tell the Jokers apart.
Once you've got two different Jokers shuffled into a deck and you've got your secret message, you're ready to start encrypting.
1. Point the deck of cards so that the face of the card showing on top is towards the ceiling. If you're used to putting decks of cards so that nobody can see the cards, just turn it upside down.
2. Find the A Joker and move him down (towards the bottom of the deck) by 1 card
3. Find the B Joker and move him down by 2 cards
(it's really important not to do those two out of order)
4. Perform a swap-cut. Take the deck-piece above the A Joker and switch it with the deck-piece below the B Joker.
(if your deck before was 1 2 3 A 4 5 6 B 7 8 9, then after it should be 7 8 9 A 4 5 6 B 1 2 3)
5. Look at the bottom card of the deck (the one closest to the table) and convert it to a number. Take the face value and add the value of the suit. Count that many cards off of the top of the deck, and place that deck-piece at the bottom of the deck, but just above the bottom card (so that the bottom card doesn't change, that's very important).
(Clubs=0, Diamonds=13, Hearts=26, Spades=39) (Ace=1, Jack=11, Queen=12, King=13)
6. Look at the top card. Convert it to a number. Count that many cards down from the top. The next card is your key-card. The numerical value of that card is the first number in your key string.
(so if your top card was the 7 of Diamonds, the 21st card in the deck would be your key-card because 7+13=20+1=21)
7. Repeat the previous steps until your key string has as many separate numbers as your message.
8. Convert your message into numbers (A=1, B=2, C=3..Z=26). DONOTUSEPC turns out to 4 15 14 15 20 21 19 5 16 3.
9. Add each corresponding digit in your keystring to your message: (keystring listed here is example)
4 15 14 15 20 21 19 5 16 3
7 12 17 14 4 2 9 1 14 4 +
————————–
11 27 31 29 24 23 28 6 30 7
10. If any number in the resulting string is above 26 (the number of letters in the alphabet), just subtract 26 from it until it isn't. This leaves us with a final string of 11 1 5 3 24 23 2 6 4 7.
11. Convert the numbers back into letters. This is your encrypted message: KAECX WBFDG
12. Do the original steps that you did with the deck of cards in reverse. Be sure to do it the same amount of times that you did it the first time.
13. Hand the deck of cards and the encrypted message to someone. They can use the same technique but subtract instead of add in the last step to get your original message back.
I have found this to be very comfy once you get the rhythm for it down. Sometimes I just sit there and generate keystrings of arbitrary length because it's very soothing. I don't even have messages to encrypt or anyone to play with.