What is the difference between known plaintext attack and chosen plaintext attack? Consider a 16-block cipher. How many possible input blocks does this cipher have? How many possible mappings are...

What is the difference between known plaintext attack and chosen plaintext

attack?

Consider a 16-block cipher. How many possible input blocks does this cipher

have? How many possible mappings are there? If we view each mapping as a

key, then how many possible keys does this cipher have?