Caesar Cipher

Note that in Sage webpages, you must evaluate the cells in order for the demonstration to work.

Here we define an alphabet:

 

Here we ‘encode’ our message in the alphabet:

 

Now we define the Shift Cryptosystem (i.e. Caesar cipher):

 

Now we can create a ciphertext out of our plaintext and a key. Here we use key=1, i.e. a shift by 1 character:

 

Now we can decipher using the same key:

 

Here’s a sandbox for you to play with:

 

Encryption

 

Decryption