Activity: Create and solve substitution ciphers
Concept:
Activity:
Binary Sequencing is a level of abstraction.
Create Your Own Abstraction.
Read about encryption ciphers below.
In a substitution cipher, each letter of the alphabet is replaced with a different letter.
A Caesar cipher is the simplest type of substitution cipher. Each letter of the alphabet is shifted
by a fixed number of places. For example, with a shift of 1, every occurrence of the letter A
becomes a B, every B becomes a C, and so on. The sequence "wraps around", so Z gets shifted
to A. The reason this cipher is so simple is that in English there are only 25 possible ways to shift
the alphabet, so it takes a maximum of 25 decoding attempts to find the original text.
For example, using a Caesar cipher with a shift of 1, HELLO becomes IFMMP. With a shift of 2,
it's JGNNQ.
An alphabet reversal cipher is another special case of a substitution cipher, where A becomes
Z, B becomes Y, C becomes X, and so on. The encoding/decoding key looks like this:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ZYXWVUTSRQPONMLKJIHGFEDCBA
Other substitution ciphers are more complicated and harder to decode. Every letter A-Z is
replaced uniquely by some other letter A-Z, but it is done randomly, not by a simple shifting of
the alphabet. You have to decode one letter at a time.
However, substitution ciphers, and Caesar ciphers in particular, don't provide any real security.
They are very easy to break and are best viewed only as fun puzzles.
Letter frequencies in the ciphered text:
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 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Go and visit this website and see what the enigma did.
http://enigmaco.de/enigma/enigma.html
I.
Choose 2 of these to try and decipher. Once you figure it out the
pattern write it down and decipher. One of these is a Caesar Cipher.
II.
III.
Come up with your own encryption code. Create a code that is at least two
sentences.
Write down the pattern. Type up the encrypted message. S
IV.
Print and see if someone can figure out your code.
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