Add Key Encapsulation Mechanism (KEM) interface

lib/src/kem.dart

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+// Copyright (c) 2020
+// Author: Hugo Pointcheval
+
+import 'dart:typed_data';
+
+import 'key.dart';
+
+enum KemMode { ENCAPSULATION, DECAPSULATION }
+
+abstract class KeyEncapsulationMechanism {
+  /// Returns the standard algorithm name for this kem
+  String get algorithm;
+
+  /// Returns the parameters used for this kem
+  Object get options;
+
+  /// Returns true if kem is initialized
+  bool get isInitialized;
+
+  /// Returns mode used in this kem.
+  KemMode get mode;
+
+  /// Returns key pair used in this kem.
+  ///
+  /// Can be an incomplete if just have public key
+  /// for example.
+  KeyPair get keypair;
+
+  /// Encapsulate key.
+  ///
+  /// Returns an [Encapsulation].
+  Future<Encapsulation> encapsulate();
+
+  /// Decapsulate key.
+  ///
+  /// Takes [Encapsulation] as parameter.
+  /// And returns plain text key as [SecretKey].
+  Future<SecretKey> decapsulate(Encapsulation encapsulation);
+}
+
+abstract class Encapsulation {
+  /// Returns the standard algorithm name used for this encapsulation
+  String get algorithm;
+
+  /// Returns the secret key used in this encapsulation
+  SecretKey get secretKey;
+
+  /// Returns the encapsulated key
+  Uint8List get key;
+}