# Research for video game: Novice cryptography concepts [closed]

I'm making a video game which has some basic cryptography as a main base for puzzle design. I'm hoping players will get great puzzle challenge and learn a few cryptography concepts through playing the game.

1. Can you suggest some of interesting areas of cryptography that would be interesting/fun/easy to learn and understand that I could use as a game mechanic?
2. Are there any instances of a single thing that are fun/interesting/unique and could be used as a puzzle?

All of these concept are masked, so that player with no experience in cryptography will ever make a connection. Some areas that are already included are basics in substitution and transposition (Caesar, Pigpen, Rail Fence, Grille...). For example of puzzle design: Grid Grille puzzle was modified in such a way that other shapes are used instead of a square, most notably 4 triangles in 1 triangle.

A few things come to mind:

1. Something based on XOR. I'm imagining an endlessly (and randomly) streaming bridge of tiles that can either be in the left position or the right position (ie the message) and you can only cross the bridge if they all line up. Straight bridge:

----------

You know that the bridge started straight, but has been XOR'd with something to make it all wonky:

-__--_--_-

and you have to find the right "key" to get the bridge back straight.

1. "Cracking a password". They have to build a cracking dictionary based on clues. Each clue adds more patterns to the dictionary, and has a better chance of cracking the password - but add too many patterns and it'll take forever! Or your "password cracking machine" only has 10 pattern slots, or something.

Edit Expanding this idea:

The math behind the number of possibilities for a password is combinatorics, but this can be hidden from the user if you want. I'm imagining that the puzzle starts with nothing known about the password and a display saying "1063 Possibilities" (which is 95^32, ie a 32 char password with all 95 printable ASCII chars). If you find a hint saying "Password is less than 16 characters" then the meter drops to 1031. Adding the hint "Contains his daughter's name "Lizzie" " drops it to 1020. And so on. When you get down to something reasonable, like 105 you get the option to brute-force.

For added fun, you could not quite give them enough hints to get them down to the brute-forceable number, making them guess the last couple hints, and maybe have to try a couple times. (This is very much how password cracking works in real life).

End Edit

1. Diffie Hellman Key Exchange is an interesting concept, and can be explored without any math (see image below). You are in a cell and can pass messages with the prisoner in the cell next to yours, but the guards can see it all. You have to coordinate your ATTACK AT DAWN without the guards catching on.

That's all I've got for now. I could probably keep going, but I should probably go to bed.

• thank you. Can you elaborate a bit more on your 2nd idea? – user3790083 Feb 15 '16 at 17:35

Depending on your video game design you maybe can utilise a many-time pad. Many-time pad is many plaintexts encrypted by XORing them with a common string.

One-time pad cannot be broken but many-time pad can, especially if the players can make an educated guess about what the plaintext message might contain.

You can also try encrypting numbers with RSA but with small modulo n so that players can easily factor it.

• Thank you for your input. I will consider you answers. But, I forgot to state that I want to evade the need to use some "boring" math, like prime numbers, exp, modulo... – user3790083 Feb 7 '16 at 18:51
• Then you may still want to consider the many time pad. Maybe disguised as a vigenere cipher but the key has the length of each message. – mandragore Feb 7 '16 at 22:21