# Math Help - Congruences

1. ## Congruences

I'm trying to solve a task from a book on Cryptography,

"Show that every nonzero congruence class mod 11 is a power of 2, and therefore 2 is a primitive root mod 11."

How should I proceed to solve this? If anyone could provide a solution that would be great. :-)

Hint: Show the order of $2$ is $\phi(11) = 11 - 1 = 10$.