A type of substitution cipher that employs multiple alphabets to enhance security is known as what?

The type of substitution cipher that employs multiple alphabets to enhance security is known as a polyalphabetic cipher. This method uses more than one alphabet to substitute characters, making it more complex and harder to break than a monoalphabetic cipher, which uses a single alphabet.

By varying the substitution of letters in a predictable manner, polyalphabetic ciphers can thwart frequency analysis, a common technique used in cryptanalysis that relies on the frequency of letters or groups of letters in the plaintext language. For example, the Vigenère cipher is a well-known polyalphabetic cipher that uses a keyword to determine which alphabet to apply for substituting each letter in the plaintext. This added complexity increases security, making it significantly more challenging for attackers to decipher the encoded message without knowledge of the keyword.

In contrast, a monoalphabetic cipher's lack of variability makes it more vulnerable to attacks since the same substitution is consistently applied, and a transposition cipher rearranges the position of characters but does not change the actual letters themselves. A one-time pad, while highly secure due to its randomness and use of a unique key, is distinctly different from a polyalphabetic cipher because it requires the key to be as long as the message and used only once. Therefore