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Secret Codes
Secret Codes
Learn how Pigpen, Caesar and Navajo Code Talkers are related in this secret code video.
The action of a Caesar cipher is to replace each plaintext letter with a different one a fixed number of places down the alphabet. The cipher illustrated here uses a left shift of three, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. Credit: Wikipedia.
Resources:
Printable Caesar Wheel:
Caesar Cipher
Caesar Cipher
Kwvozibctibqwva, gwc lmkqxpmzml bpm kwlm!
The line above appears to be gibberish, but to a trained eye, it is a secret code.
The Caesar Cipher shifts each letter a fixed number of times forwards or backwards. This simple form of encryption gets its name from Julius Caesar who used it in personal correspondences.
Here is an example of a cipher with a shift of 3.
Plain: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Cipher: X Y Z A B C D E F G H I J K L M N O P Q R S T U V W
Each letter is shifted forward three times.
"D" becomes "A"
"Z" becomes "W".
The trailing letters of the alphabet get shifted to the beginning.
"A" becomes "X" and so forth.
A message is written in plain text and then ciphered using a key like the one above or a cipher wheel that can be turned to correspond to the number of shifts.
Message: Breakfast is the most important meal of the day.
Cipher: Yobxhcxpq fp qeb jlpq fjmloqxkq jbxi lc qeb axv.
Incorporating Mathematics
Incorporating Mathematics
From the NRICH Team at Cambridge University:
Click here for the full source.
This all seems very clever, but so far it's all been letters and no numbers. So where's the maths? The maths comes if you think of the letters as numbers from 0 to 25 with A being 0, B being 1, C being 2 etc. Then encoding, shifting the alphabet forward three places, is the same as adding three to your starting number:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
For example, encoding the letter 'A' is 0+3=3, which is a 'D'.
Coding 'I' is: 8+3=11, which is 'L'.
However, you do have to be careful when you get to the end of the alphabet, because there is no letter number 26, so you have to go back to number 0. In maths we call this 'MOD 26', instead of writing 26, we go back to 0.
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