# Caesar Cipher (Python) I’m having a play in Python today and looking at the Caesar Cipher.

The Caesar Cipher (Caesar Shift, Caesar’s Code) is a simple, easy to implement substitution cipher. The cipher is named after Julius Caesar. The cipher works by taking the letters of the message and then shifts the letter a defined space along the alphabet.

For example a shift of 1 character would make a=b, b=c, c=d etc.

I’m making a program with Python that can encrypt or decrypt a text message using the Caesar Cipher.

——

#Caesar Cipher

#GeekTechStuff

letters=”ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ”

encrypt=input(“Do you want to encrypt a message? (Y/N):”)

encrypt=encrypt.upper()

if encrypt == “Y”:

stringtoencrypt=input(“Please enter A-Z characters to encrypt:”)

stringtoencrypt=stringtoencrypt.upper()

ciphershift=input(“Please enter a number between 1 and 25 to be your cipher key: “)

ciphershift=int(ciphershift)

stringencrypted=””

for character in stringtoencrypt:

position = letters.find(character)

newposition = position+ciphershift

if character in letters:

stringencrypted = stringencrypted + letters[newposition]

else:

stringencrypted = stringencrypted + character

ciphershift=str(ciphershift)

print(“You used a cipher shift of “+ciphershift)

print(stringencrypted)

if encrypt == “N”:

stringtodecrypt=input(“Please enter A-Z characters to dencrypt:”)

stringtodecrypt=stringtodecrypt.upper()

ciphershift=input(“Please enter a number between 1 and 25 to be your cipher key: “)

ciphershift=int(ciphershift)

stringdecrypted=””

for character in stringtodecrypt:

position = letters.find(character)

newposition = position-ciphershift

if character in letters:

stringdecrypted = stringdecrypted + letters[newposition]

else:

stringdecrypted = stringdecrypted + character

ciphershift=str(ciphershift)

print(“You used a cipher shift of “+ciphershift)

print(stringdecrypted)

else:

print(“Ending Caesar Cipher”)