Vigenere Cypher

Program File Name: vigenere.py

Author: Tyler S. Budd

Completion Date: 9/12/2019

Description:

A modified version of the classic Vigenere Cypher. Instead of using just letters that are confined to uppercase or lowercase, I've allowed it to accept all ASCII characters from 32 [space] to 126 [~]. This gives the message much more security and much harder to crack with human eyes.

Mathematical Approach:

At first, I was going to approach the problem by creating the matrix and using the analog "search and find" method, like what we would use in the image below. Instead, I found a better approach to use only mathematics.

For example, if we were to encrypt a message with only the original 26x26 matrix, I would use the formula:

• Encryption(i) = (Plaintext(i) + Key(i)) mod 26
  • i = index of the string

To decode, I use the formula:

• Decryption(i) = (Encryption(i) - Key(i) + 26) mod 26
  • i = index of the string

Because I used 94 ASCII characters as my matrix, I modified the formulas.

Program Demo

Welcome to the Vigenere Cypher Program!
Created by: TYLER S. BUDD
Creation date: September 12th, 2021
NOTE: This encryption program only encrypts/decrypts letters, numbers, and basic punctuation. 
      Any symbol/letter not found on a US keyboard will result in failure.

To ENCRYPT a message, type 'encrypt' and press ENTER
To DECRYPT a message, type 'decrypt' and press ENTER

Selection: encrypt

COPY/PASTE or TYPE plaintext message here and press ENTER:      this is a test

Type in the key phrase to encrypt and press ENTER:      holiday

Encrypted Message:    ^RS]hS]hKh^O]^

To close the program press Ctrl+C

Copy the encrypted message: ^RS]hS]hKh^O]^

Restart the program

Welcome to the Vigenere Cypher Program!
Created by: TYLER S. BUDD
Creation date: September 12th, 2021
NOTE: This encryption program only encrypts/decrypts letters, numbers, and basic punctuation. 
      Any symbol/letter not found on a US keyboard will result in failure.

To ENCRYPT a message, type 'encrypt' and press ENTER
To DECRYPT a message, type 'decrypt' and press ENTER

Selection: decrypt

COPY/PASTE or TYPE encrypted message here and press ENTER:      ^RS]hS]hKh^O]^

Type in the key phrase to decrypt and press ENTER:      holiday

Decrypted Message:      this is a test

To close the program press Ctrl+C

Additional Material:

94x94 ASCII matrix used available on the file vigenereCypherMatrix.txt

Original 26x26 Matrix and encoding example: