More decoy documenation

protocol/src/lib.rs

@@ -248,7 +248,6 @@ impl PacketReader {
         content_slice[0..3].copy_from_slice(&enc_content_len);
         let content_len = u32::from_le_bytes(content_slice);
 
-        // Include 1-byte decoy and 16-byte tag.
         content_len as usize + NUM_HEADER_BYTES + NUM_TAG_BYTES
     }
 
@@ -258,7 +257,8 @@ impl PacketReader {
     ///
     /// * `ciphertext` - The message from the peer excluding the first 3 length bytes. It should contain
     ///                  the header, contents, and authentication tag.
-    /// * `contents`   - Mutable buffer to write plaintext.
+    /// * `contents`   - Mutable buffer to write plaintext. Note that the first byte is the header byte
+    ///                  containing protocol flags.
     /// * `aad`        - Optional associated authenticated data.
     ///
     /// # Returns
@@ -327,7 +327,7 @@ impl PacketReader {
         match self.decrypt_contents(ciphertext, &mut contents, aad)? {
             PacketType::Decoy => Ok(None),
             PacketType::Genuine => {
-                // Drop the decoy byte flag.
+                // Drop the header byte.
                 contents.remove(0);
                 Ok(Some(contents))
             }
@@ -375,19 +375,19 @@ impl PacketWriter {
         }
 
         let plaintext_length = plaintext.len();
-        let decoy_index = NUM_LENGTH_BYTES + NUM_HEADER_BYTES - 1;
-        let plaintext_start_index = decoy_index + 1;
+        let header_index = NUM_LENGTH_BYTES + NUM_HEADER_BYTES - 1;
+        let plaintext_start_index = header_index + 1;
         let plaintext_end_index = plaintext_start_index + plaintext_length;
 
-        // Set decoy byte.
-        packet[decoy_index] = packet_type.to_byte();
+        // Set header byte.
+        packet[header_index] = packet_type.to_byte();
         packet[plaintext_start_index..plaintext_end_index].copy_from_slice(plaintext);
 
-        // Encrypt decoy byte and plaintext in place and produce tag.
+        // Encrypt header byte and plaintext in place and produce authentication tag.
         let auth = aad.unwrap_or_default();
         let tag = self
             .packet_encoding_aead
-            .encrypt(auth, &mut packet[decoy_index..plaintext_end_index]);
+            .encrypt(auth, &mut packet[header_index..plaintext_end_index]);
 
         // Encrypt plaintext length.
         let mut content_len = [0u8; 3];