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GeoGebraGeoGebra Classroom

Cryptography and Coordinates

Your school prohibits using cellphones during school hours, but you and your friends found a way to communicate using encrypted messages, so that just those who have the key can understand the content of the message. Here is your key! It's a grid, containing all the letters of the alphabet. Each letter has its own coordinates, and only who has the same exact grid can decode the message.

The Signature

Every message must be signed, in order to understand who is the sender. My signature is . What is yours?

Separating Words

An encrypted message must be understandable though! We will separate words by enclosing each one of them in braces. Write an encrypted message to a classmate.

Securing Data

Securing data is the core principle on which cryptography methods are based. If we used as key just the x-coordinates of the points that you see in the grid, would this method be as safe as the original one? And what if we used only y-coordinates? If you had to choose between x-coordinates or y-coordinates only to encrypt your message, which of the two methods would be the most efficient and safe? Explain your choice in detail.

Create Your Own Decryption Grid

Drag the points in the app below to create your own decryption grid. Points must respect the following conditions: - each point must have unique coordinates - the x-coordinate of the vowels is -1 - the x-coordinate of D is -6 - the x-coordinate of H and K is -5 - points W, X, Y and Z belong to the y-axis - points L, M, N, R, S and T belong to the x-axis - the y-coordinate of B, F, J, P and V is 3 - points C, G, and Q have their x-coordinate equal to their y-coordinate