Fixing minor nits: conversion to u16 and removing keypair constructor

deny.toml

@@ -44,7 +44,7 @@ yanked = "warn"
 # The lint level for crates with security notices. Note that as of
 # 2019-12-17 there are no security notice advisories in
 # https://github.com/rustsec/advisory-db
-notice = "warn"
+notice = "deny"
 # A list of advisory IDs to ignore. Note that ignored advisories will still
 # output a note when they are encountered.
 ignore = [

src/key_exchange/tripledh.rs

@@ -25,6 +25,7 @@ use generic_bytes::SizedBytes;
 use hkdf::Hkdf;
 use hmac::{Hmac, Mac, NewMac};
 use rand::{CryptoRng, RngCore};
+use std::convert::TryFrom;
 use zeroize::Zeroize;
 
 const KEY_LEN: usize = 32;
@@ -493,7 +494,9 @@ fn hkdf_expand_label_extracted<D: Hash>(
     let mut okm = vec![0u8; length];
 
     let mut hkdf_label: Vec<u8> = Vec::new();
-    hkdf_label.extend_from_slice(&length.to_be_bytes()[std::mem::size_of::<usize>() - 2..]);
+
+    let length_u16: u16 = u16::try_from(length).map_err(|_| PakeError::SerializationError)?;
+    hkdf_label.extend_from_slice(&length_u16.to_be_bytes());
 
     let mut opaque_label: Vec<u8> = Vec::new();
     opaque_label.extend_from_slice(STR_OPAQUE);

src/keypair.rs

@@ -76,16 +76,6 @@ impl<G: Group> KeyPair<G> {
         &self.sk
     }
 
-    /// A constructor that receives public and private key independently as
-    /// bytes
-    pub fn new(public: PublicKey, private: PrivateKey) -> Result<Self, InternalPakeError> {
-        Ok(Self {
-            pk: public,
-            sk: private,
-            _g: PhantomData,
-        })
-    }
-
     /// Generating a random key pair given a cryptographic rng
     pub(crate) fn generate_random<R: RngCore + CryptoRng>(rng: &mut R) -> Self {
         let sk = G::random_nonzero_scalar(rng);
@@ -131,7 +121,11 @@ impl<G: Group> KeyPair<G> {
     pub fn from_private_key_slice(input: &[u8]) -> Result<Self, InternalPakeError> {
         let sk = PrivateKey(Key::from_arr(GenericArray::from_slice(input))?);
         let pk = Self::public_from_private(&sk);
-        Self::new(pk, sk)
+        Ok(Self {
+            pk,
+            sk,
+            _g: PhantomData,
+        })
     }
 
     #[cfg(test)]