The mapping from plaintext character to ciphertext character in polyalphabetic substitution is one-to-many.

Kasiski Method attacks Vigenere cipher by guessing the key length through repeated ciphertext.

In one-time pad, the key can be used at most twice.

Letter frequency analysis was used to cryptanalyse monoalphabetic substitution ciphers.

Vigenère Cipher is a polyalphabetic substitution cipher based on the concept of multiple Caesar ciphers.

Product ciphers in general are less secure than substitution and transposition ciphers.

One important step for cryptanalysing transposition ciphers is by guessing the period.

Playfair cipher is more secure than monoalphabetic substitution cipher.

The frequency distribution of the plaintext and ciphertext is not the same for a transposition cipher.