D: Informatics

Secure Communication

If you input any personal information online, you can usually assume that such information would be encrypted and kept private. Often time, communication needs to be secure. In Meeting 1, we explored different ways of coding sentences such that others without the coding key would not be able to decode and read the sentences.

A Secret Message

Our secret agent, Agent A., just sent us a video message.

Can you understand it? What do these pictures mean? Is this an important message? Luckily, Agent A. also transmitted via satellite the following coded phrase:

Your task: unscramble the message using the following key:

For each number in the message, do the following in order:

(1) Add 1
(2) Multiply by 3
(3) Take the remainder after dividing by 10. (This is called ‘modulo 10.’ Ex: the remainder of 92 modulo 10 is 2.)

You can do this on this Google Sheet. What do you find? Can you make sense of this now? What does the message say? Is Agent A in danger and need our help?

Hint: Agent A. is very imaginative and likes to associate numbers with letters. For examples

0 = O , 1 = I , 3 = E , 4 = A , . . . .

Points Assignment: Earn +1 point for each letter decoded in the message. Earn +10 points for reading out the whole message.