Introducing a trait for key exchange (#20)

src/key_exchange/traits.rs

@@ -0,0 +1,55 @@
+// 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.
+
+use crate::{
+    errors::{InternalPakeError, ProtocolError},
+    keypair::{Key, KeyPair},
+};
+use rand_core::{CryptoRng, RngCore};
+
+use std::convert::TryFrom;
+
+pub trait KeyExchange {
+    type KE1State: TryFrom<Vec<u8>, Error = InternalPakeError> + ToBytes;
+    type KE2State: TryFrom<Vec<u8>, Error = ProtocolError> + ToBytes;
+    type KE1Message: TryFrom<Vec<u8>, Error = InternalPakeError> + ToBytes;
+    type KE2Message: TryFrom<Vec<u8>, Error = ProtocolError> + ToBytes;
+    type KE3Message: TryFrom<Vec<u8>, Error = ProtocolError> + ToBytes;
+
+    fn generate_ke1<R: RngCore + CryptoRng, KeyFormat: KeyPair<Repr = Key>>(
+        l1_component: Vec<u8>,
+        rng: &mut R,
+    ) -> Result<(Self::KE1State, Self::KE1Message), ProtocolError>;
+
+    fn generate_ke2<R: RngCore + CryptoRng, KeyFormat: KeyPair<Repr = Key>>(
+        rng: &mut R,
+        l1_bytes: Vec<u8>,
+        l2_bytes: Vec<u8>,
+        ke1_message: Self::KE1Message,
+        client_s_pk: KeyFormat::Repr,
+        server_s_sk: KeyFormat::Repr,
+    ) -> Result<(Self::KE2State, Self::KE2Message), ProtocolError>;
+
+    fn generate_ke3<KeyFormat: KeyPair<Repr = Key>>(
+        l2_component: Vec<u8>,
+        ke2_message: Self::KE2Message,
+        ke1_state: &Self::KE1State,
+        server_s_pk: KeyFormat::Repr,
+        client_s_sk: KeyFormat::Repr,
+    ) -> Result<(Vec<u8>, Self::KE3Message), ProtocolError>;
+
+    fn finish_ke(
+        ke3_message: Self::KE3Message,
+        ke2_state: &Self::KE2State,
+    ) -> Result<Vec<u8>, ProtocolError>;
+
+    fn ke1_state_size() -> usize;
+
+    fn ke2_message_size() -> usize;
+}
+
+pub trait ToBytes {
+    fn to_bytes(&self) -> Vec<u8>;
+}