[ORTHOGONAL] Add docs to identity_key!

rust/protocol/src/identity_key.rs

@@ -1,8 +1,10 @@
 //
-// Copyright 2020 Signal Messenger, LLC.
+// Copyright 2020-2021 Signal Messenger, LLC.
 // SPDX-License-Identifier: AGPL-3.0-only
 //
 
+//! Wrappers over identity primitives from [crate::curve].
+
 use crate::proto;
 use crate::{KeyPair, PrivateKey, PublicKey, Result, SignalProtocolError};
 
@@ -11,6 +13,7 @@ use std::convert::TryFrom;
 
 use prost::Message;
 
+/// Wrapper for [PublicKey].
 #[derive(Debug, PartialOrd, Ord, PartialEq, Eq, Clone, Copy)]
 pub struct IdentityKey {
     public_key: PublicKey,
@@ -51,20 +54,23 @@ impl From<PublicKey> for IdentityKey {
     }
 }
 
+/// Wrapper for [KeyPair].
 #[derive(Copy, Clone)]
 pub struct IdentityKeyPair {
     identity_key: IdentityKey,
     private_key: PrivateKey,
 }
 
 impl IdentityKeyPair {
+    /// Create a new key pair from a public `identity_key` and a private `private_key`.
     pub fn new(identity_key: IdentityKey, private_key: PrivateKey) -> Self {
         Self {
             identity_key,
             private_key,
         }
     }
 
+    /// Generate a cryptographically random new identity from randomness in `csprng`.
     pub fn generate<R: CryptoRng + Rng>(csprng: &mut R) -> Self {
         let keypair = KeyPair::generate(csprng);