The Vigenere cipher is an example of which type of cipher?

The Vigenere cipher is classified as a polyalphabetic cipher, which means it uses multiple substitution alphabets to encrypt the data. In a polyalphabetic cipher, the same letter can be encrypted to different letters depending on its position in the text or based on a key that varies the substitution.

In the case of the Vigenere cipher, a keyword is employed to determine which alphabet to use for each letter of the plaintext. This characteristic of rotating through different substitution methods based on the keyword makes it resistant to frequency analysis, which is a common technique used to break simpler substitution ciphers that only use a single alphabet throughout the entire message.

This cipher's complexity provides a more secure method of encryption compared to simpler techniques, such as monoalphabetic substitution ciphers, which maintain a single substitution pattern for all occurrences of a letter. Understanding the Vigenere cipher as a polyalphabetic cipher highlights its innovative approach to encryption, enabling a more sophisticated level of data protection in historical contexts.