Vigenère cipher

The Vigenère cipher is a method of encrypting text by applying a series of shifts based on a keyword. Each letter of the message is shifted forward in the alphabet by a number determined by the corresponding letter of the keyword. When the keyword is shorter than the message, it repeats. This creates a complex pattern that makes it harder for someone without the key to decode the message. It's a classical technique used historically for secure communication, relying on the idea of shifting letters uniquely based on the key to obfuscate the original message.