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

Here we define an alphabet:

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alphabet = AlphabeticStrings() 

alphabet.gens()

Here we ‘encode’ our message in the alphabet:

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plaintext = alphabet.encoding("We are the champions.") 

plaintext

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

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system = ShiftCryptosystem(alphabet) 

system

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:

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key = 1 

ciphertext = system.enciphering(key, plaintext) 

ciphertext

Now we can decipher using the same key:

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plaintextrecovered = system.deciphering(key, ciphertext) 

plaintextrecovered

Here’s a sandbox for you to play with:

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alphabet = AlphabeticStrings() 

plaintext = alphabet.encoding("We are the champions.") 

system = ShiftCryptosystem(alphabet) 

key = 1 

ciphertext = system.enciphering(key, plaintext) 

plaintextrecovered = system.deciphering(key, ciphertext) 

plaintextrecovered

Encryption

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alphabet = AlphabeticStrings() 

plaintext = alphabet.encoding("We are the zucchini.") 

system = ShiftCryptosystem(alphabet) 

key = 1

ciphertext = system.enciphering(key, plaintext) 

ciphertext

Decryption

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alphabet = AlphabeticStrings() 

ciphertext = alphabet.encoding("XFBSFUIFAVDDIJOJ") 

system = ShiftCryptosystem(alphabet) 

key = 1 

plaintext = system.deciphering(key, ciphertext) 

plaintext