$2$

$0/1$ point

What is the main reason that RSA is a secure encryption system? In other words, if a public $($encryption$)$ key $(n,e)$ is available, why is it difficult to find the decryption key?

The decryption key can be chosen completely at random, so it is very difficult to guess it$.$

It is not difficult $-$ we did it in class!

It is easy to find $(n)=(p-1)(q-1),$ but it is very difficult to find the inverse of $e$ modulo $(p-1)(q-1).$

The decryption key requires that the prime factorization on $n$ be known, but prime factorizations are very difficult to compute when the prime numbers are large.