Coding by Vigenère cipher

Blaise de Vigenère

The Vigenère cipher is a method of text protection by encrypting, based on an alphabet and a series of Caesar ciphers in the tabula recta, than on the letters in keyword. It is a simple form of polyalphabetic substitution.

Here is reserved the standard form of Vigenère cipher, but with the Alphabet that consists of a series of ten digits and 26 lowercase than uppercase of the English letters. Letters out of the Alphabet are ignored, i.e. not encoded. Letters of the keywords should be in the Alphabet.

Encryption is the process of converting text into a code, especially to prevent unauthorized access. Decryption is the process of converting encrypted data back into its original text. Keyword is a word that acts as the password of the code.

Alphabet: 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ


How it works

In a Caesar cipher, each letter of the alphabet is shifted along some number of places. In Vigenere cipher we have sequence of Caesar's alphabet each shifted by one letter to the previous and formed the tabula recta. You enter a plaintext, and a keyword that has been repeated into keytext, so it matches the length of the plaintext. The n-th letter of plaintext is enciphered using the alphabet in the row that start by the same letter. Than the letter in plaintext is changed by the letter in keytext, and so on until you got ciphertext. Decryption is performed backward, by finding the position of the ciphertext letter in a row of the table, and then taking the label of the column in which it appears as the plaintext.