Research for video game: Novice cryptography concepts 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.


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?
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.
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.