Problem 1

The following plaintext MAJORCONTRIBUTIONWASTHEUSEOFMATH was encrypted by Hill Cipher with 2X2 key matrix and the correspondent ciphertext is KWHGLIDRQVRPFRECPQEGIJCOAEHXKWI. Find a key matrix.

Problem 2

The ciphertext is VFCKOLQOBPTEJENAFJCHBEXS
Part of plaintext is lessplastic
Find Matirx Key and decrypt the message.

Problem 3

The ciphertext is KGYXSH
Part of plaintext is MASTER
Find Matirx Key, IF POSSIBLE. EXPLAIN!

Problem 4

Give an example of the plaintext/ciphertext pair for which it is impossible to find the key.