Introducing a trait for key exchange (#20)

src/key_exchange/mod.rs

@@ -0,0 +1,10 @@
+// Copyright (c) Facebook, Inc. and its affiliates.
+//
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+
+//! Includes instantiations of key exchange protocols used in the
+//! login step for OPAQUE
+
+pub(crate) mod traits;
+pub mod tripledh;