Hello, I am struggling with cryptology questions for my understanding.

Problem 2 [41: Definitions Provide a formal definition of the Gen, Enc, and Dec algorithms for both the mono-alphabetic substitution and Vigenre ciphers. Problem 3 [4]: Improving Vigenre Consider an improved version of the Vigenre cipher, where instead of using multiple shift ciphers, multiple mono-alphabetic substitution ciphers are used. That is, the key consists of t random permutations of the alphabet and the plaintext characters in positions i; t+i; 2t+i, and so on are encrypted using the ith permutation. Discuss informally how to break this version of the cipher Problem 4 [6]: Known plaintext attacks Show that the shift, substitution, and Vigenre ciphers are all trivial to break using a known-plaintext attack. How much known plaintext is needed to completely recover the key for each of the ciphers? Problem 5 [6]: Chosen plaintext attacks Show that the shift, substitution, and Vigenre ciphers are all trivial to break using a chosen-plaintext attack. How much plaintext must be encrypted in order for the adversary to completely recover the key? Compare to the previous