Wednesday

Number cipher

A number cypher takes a word and converts all charcters to numbers. The numbers are equal to the order of the character in the alphabeat. Here is an example:

abc -> 1;2;3
ben -> 2;5;14
hello -> 8;5;12;12;15

Physically encode a message and send it to a receiver in another group. Verify if they got the right answer!

See if everyone can get to both encode (word to code) and decode (code to word)

Caesar cipher

Caesar cypher works similar to number cypher. Now instead of just encoding a message to numbers, we encode them to new characters. But the new characters are shifted 3 to the right. Watch this video that explains the process super well: https://youtu.be/o6TPx1Co_wg

This video is also really good: https://www.youtube.com/watch?v=sMOZf4GN3oc

https://youtu.be/Kf9KjCKmDcU

Now you will have to make a physical Caesar cypher 👇

Here are some examples:

abc -> def
ben -> ehq
Hello -> khoor

Cæsar 1

Cæsar 2

Cæsar 3

Cæsar 4

Cæsar 5

Try to both encode a message and decode a message. That means

• Send a message to a person in another group. Can they correctly decode your message?

• Receive a message from someone in another group. Can you decode that correctly?

• Now try and play around with

  • Shift number - What if you instead of shifting 3 shifted 5 or 15. How would that look

  • Shift direction - What if you instead of shifting to the right shifted to the left

  • Encode a message where you send the shift number and shift direction with it. Can they still get the correct message?

Let's get coding!

Let's build some encryption helper methods!

characterToIndex

This method will be used for encoding our message!

Create a method called characterToIndex. The method takes a character and returns the index.

Remember the index for number cypher starts at 1 not 0!

int indexOfCharacterA = characterToIndex('a');
System.out.println(indexOfCharacterB); // 1

int indexOfCharacterE = characterToIndex('e');
System.out.println(indexOfCharacterB); // 5

indexToCharacter

This method will be used for decoding our message!

Create a method called indexToCharacter. The method takes an integer and returns the character for that index.

Remember the index for number cypher starts at 1 not 0!

char characterForindex1 = indexToCharacter(1);
System.out.println(characterForindex1); // a

int characterForindex5 = indexToCharacter(5);
System.out.println(characterForindex5); // e

ceasarCharacterEncoder

This is the method that will help encode our message!

ceasarCharacterEncoder should take a character and return a new encoded character using the Caesar cypher:

char CharacterBEncoded = ceasarCharacterEncoder('b');
System.out.println(CharacterBEncoded); // e

char CharacterYEncoded = ceasarCharacterEncoder('y');
System.out.println(CharacterYEncoded); // b

Consider using modulus for this task

ceasarCharacterDecoder

This is the method that will help decode our message!

ceasarCharacterDecoder should take a encoded character and return a new decoded character using the Caesar cypher:

char CharacterEEncoded = ceasarCharacterEncoder('e');
System.out.println(CharacterEEncoded); // b

char CharacterBEncoded = ceasarCharacterEncoder('b');
System.out.println(CharacterBEncoded); // y

Consider using modulus for this task

Projecttime

You can now start on the project!