Caesar Cipher

Caesar_Cipher It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabets

how it worksThe transformation can be represented by aligning two alphabets; the cipher alphabet is the plain alphabet rotated left or right by some number of positions. For instance, here is a Caesar cipher using a left rotation of three places, equivalent to a right shift of 23 (the shift parameter is used as the key):

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 When encrypting, a person looks up each letter of the message in the "plain" line and writes down the corresponding letter in the "cipher" line.

Plaintext: THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG Ciphertext: QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD Deciphering is done in reverse, with a right shift of 3.

The replacement remains the same throughout the message, so the cipher is classed as a type of monoalphabetic substitution, as opposed to polyalphabetic substitution.

how to work with: use encrypt.py to encrpt any message file and decrypt to decrypt it. the key is stored in the code but can be stored in the form of a file and moved around as well.

for example: to encrypt message.txt you will do: python3 encrypt.py message.txt you can use any file name there (the original file will be deleted after encryption) to decrypt you can do python3 decrypt.py encrypted_message.txt and you will get your original message back.

Built With

• python