add text on how to hide message lengths...

twistednoise.py

@@ -45,6 +45,20 @@ __license__ = '2-clause BSD license'
 # Notes:
 # Using XK, so that the connecting party's identity is hidden and that the
 # server's party's key is known.
+#
+# Noise packets are 16 bytes + length of data
+#
+# Proposed method to hide message lengths:
+# Immediately after handshake completes, each side generates and sends
+# an n byte key that will be used for encrypting (algo tbd) their own
+# byte counts.  The length field will be encrypted via
+# E(pktnum, key) XOR 2 byte length.
+#
+# Note that authenticating the message length is NOT needed.  This is
+# because the noise message blocks themselves are authenticated.  The
+# worse that could happen is that a larger read (64k) is done, and then
+# the connection aborts because of decryption failure.
+#
 
 def genkeypair():
 	'''Generates a keypair, and returns a tuple of (public, private).