update primitive docs.
/// A general purpose API for Cryptographic Primitives.
-/// This crate's aim is to provide an abstraction layer that allows you to swap the backend easily.
+/// This crate's aim is to provide an abstraction layer with extensible cryptographic primitives. Each primitive
+/// contains an info data structure for describing the constraints of the algorithm and at least one trait.
/// Message Auth Code
pub mod auth;
