The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. To encrypt, each letter of the plaintext is shifted along the alphabet by the position of the corresponding letter in the keyword. The keyword is repeated to match the length of the message. For example, if the keyword is "KEY" and the message is "HELLO", each letter is shifted according to "K", "E", and "Y". This makes the cipher more secure than a simple Caesar cipher because the same letter may be encrypted differently depending on its position in the text. However, it can be broken with frequency analysis if the keyword is short.
