This doth be a machine-wrought text which may contain errors!
Theory
Now shall we behold a thing far more complex than the Cæsar cipher, even polyalphabetic ciphers! As the name doth perchance reveal unto some of ye, poly, in comparison with mono, signifieth many instead of single.
The Cæsar cipher, for example, did employ but “one” alphabet, monoalphabetic. Polyalphabetic ciphers do use divers at once. We shall begin by beholding one of the simplest, since it doth naturally follow from the Cæsar cipher, the Vigenère cipher.
How doth this work? Behold the following figure:
This is a table of how Vigenère doth determine its encryption. It doth tell thee naught, perchance, but here is a brief explanation:
The Vigenére Cipher
The Vigenére cipher doth employ a keyword to determine how a thing shall be encrypted and decrypted.
An example of a keyword may be, for instance, LEMON. The keyword doth perform thus:
Example
Take a text, an example herein: Hallo, alle sammen! I dag skal vi ha om enkryptering!. The first step, prithee, remove all spaces, special characters, and render all unto uppercase. Then shall we take the key LEMON and repeat it unto the very end of the text:
HALLOALLESAMMENIDAGSKALVIHAOMENKRYPTERING
LEMONLEMONLEMONLEMONLEMONLEMONLEMONLEMONL
The key is used to encrypt each individual letter by means of the Caesar cipher.
The letter A is a rotation of 0, B a rotation of 1, C with 2, D with 3, and so forth.
Thus, the text is encrypted unto:
SEXZBLPXSFLQYSATHMUFVEXJVSEAARYODMCEIDWAR
| Letter | Rotation | Result |
| -------- | -------- | -------- |
|
H|L(11) |S||
A|E(4) |E||
L|M(12) |X||
L|O(14) |Z||
O|N(13) |B||
A|L(11) |L||
L|E(4) |P|| … | … | … |
🚧🚧 Work in progress! 🚧🚧
Tasks
Task the First – Vigenère Ciphering
Implement, pray thee, the Vigenère Cipher.