09

Challenge 09 - Encryption scheme

An encryption scheme consists of a set $\{E_e:e \in K\}$ and a corresponding set $\{D_d: d \in K\}$ of encrypting and decrypting functions, respectively. For each $e \in K$, there is a unique key $d \in K$ where $D_d=E_e^{-1}$. An encryption scheme is also called a cipher.

It should be clear that every $e$ is actually a representative of some bijection from $M$ to $C$. In this task, you have to count the number of such bijections and, hence, the number of keys that produce different encryption functions.

Assume that $|M|=|C|=n$ which is given as the input.

differentEncryptions(3) // 6

Constraints:

• $1 \leq n \leq 10$

Solutions

• Go (Golang)