Add async "constructors" for key generation

lib/src/key.dart

@@ -9,6 +9,8 @@ import 'platform.dart';
 
 import 'exceptions.dart';
 import 'keyspec.dart';
+import 'cipher.dart';
+import 'utils.dart';
 
 /// This is the base class of all key types.
 abstract class Key {
@@ -33,21 +35,21 @@ abstract class Key {
 /// This represents a secret key, usefull in
 /// algorithms like AES or BlowFish.
 class SecretKey extends Key {
-  List<String> _supportedAlgorithms = ["AES", "Blowfish"];
-
   /// Creates a key from raw byte array
-  SecretKey.fromBytes(Uint8List bytes) : super(bytes: bytes);
+  SecretKey.fromBytes(Uint8List bytes,
+      {CipherAlgorithm algorithm: CipherAlgorithm.None})
+      : super(bytes: bytes, algorithm: algorithm.name);
 
   /// Creates a key from a specific size.
-  SecretKey.generate(String algorithm, int size) {
-    if (!_supportedAlgorithms.contains(algorithm)) {
-      throw KeyException(algorithm + " not supported!");
-    } else if (algorithm == "AES") {
-      List<int> supportedSizes = [128, 192, 256];
-      if (!supportedSizes.contains(size)) {
+  static Future<SecretKey> generate(int size, CipherAlgorithm algorithm) async {
+    if (algorithm == null) {
+      throw KeyException("Algorithm can't be null");
+    } else if (algorithm == CipherAlgorithm.AES) {
+      List<int> _supportedSizes = [128, 192, 256];
+      if (!_supportedSizes.contains(size)) {
         throw KeyException("AES must be 128, 192 or 256 bits long.");
       }
-    } else if (algorithm == "Blowfish") {
+    } else if (algorithm == CipherAlgorithm.BlowFish) {
       List<int> supportedSizes =
           List<int>.generate(52, (int index) => (index + 4) * 8);
       if (!supportedSizes.contains(size)) {
@@ -55,15 +57,12 @@ class SecretKey extends Key {
             "Blowfish must be between 4 and 56 bytes (32 and 448 bits) long.");
       }
     }
-    _generate(algorithm, size);
-  }
 
-  Future<void> _generate(String algo, int size) async {
     try {
-      _bytes = await Platform().keygen(size);
-      _algo = algo;
-      log("Generated SecretKey size: ${_bytes.length * 8} bits (${_bytes.length} bytes)",
+      Uint8List _key = await Platform().keygen(size);
+      log("Generated SecretKey size: ${_key.length * 8} bits (${_key.length} bytes)",
           name: "NativeCrypto");
+      return SecretKey.fromBytes(_key, algorithm: algorithm);
     } on PlatformException catch (e) {
       log(e.message, name: "NativeCrypto");
       throw KeyException(e);

lib/src/sym/AES.dart

@@ -12,15 +12,29 @@ import '../utils.dart';
 /// Defines all available key sizes.
 enum AESKeySize { bits128, bits192, bits256 }
 
+extension AESKeySizeExtension on AESKeySize {
+  int get length {
+    int l;
+    switch (this) {
+      case AESKeySize.bits128:
+        l = 128;
+        break;
+      case AESKeySize.bits192:
+        l = 192;
+        break;
+      case AESKeySize.bits256:
+        l = 256;
+        break;
+    }
+    return l;
+  }
+}
+
 class AESCipher implements Cipher {
   SecretKey _sk;
   CipherParameters _params;
   bool _isInit;
 
-  List<CipherParameters> _supportedCipherParams = [
-    CipherParameters(BlockCipherMode.CBC, Padding.PKCS5),
-  ];
-
   @override
   CipherAlgorithm get algorithm => CipherAlgorithm.AES;
 
@@ -33,34 +47,31 @@ class AESCipher implements Cipher {
   @override
   bool get isInitialized => _isInit;
 
+  @override
+  List<CipherParameters> get supportedParameters => [
+        CipherParameters(BlockCipherMode.CBC, PlainTextPadding.PKCS5),
+      ];
+
   /// Creates an AES cipher with specified secretKey and mode/padding
   AESCipher(SecretKey secretKey, CipherParameters parameters) {
-    if (secretKey.algorithm != "AES") {
-      throw CipherInitException("Invalid key type: " + secretKey.algorithm);
-    } else if (!_supportedCipherParams.contains(parameters)) {
+    if (secretKey.algorithm != CipherAlgorithm.AES.name) {
+      List<int> _supportedSizes = [128, 192, 256];
+      if (!_supportedSizes.contains(secretKey.encoded.length)) {
+        throw CipherInitException("Invalid key length!");
+      }
+    } else if (!supportedParameters.contains(parameters)) {
       throw CipherInitException("Invalid cipher parameters.");
     }
+    _sk = secretKey;
     _params = parameters;
     _isInit = true;
   }
 
   /// Generates a secret key of specified size, then creates an AES cipher.
-  AESCipher.generate(AESKeySize size, CipherParameters parameters) {
-    Map<AESKeySize, int> _supportedSizes = {
-      AESKeySize.bits128: 128,
-      AESKeySize.bits192: 192,
-      AESKeySize.bits256: 256
-    };
-
-    if (!_supportedCipherParams.contains(parameters)) {
-      throw CipherInitException("Invalid cipher parameters.");
-    } else if (!_supportedSizes.containsKey(size)) {
-      throw CipherInitException("Invalid key size.");
-    }
-
-    _sk = SecretKey.generate("AES", _supportedSizes[size]);
-    _params = parameters;
-    _isInit = true;
+  static Future<AESCipher> generate(
+      AESKeySize size, CipherParameters parameters) async {
+    SecretKey _sk = await SecretKey.generate(size.length, CipherAlgorithm.AES);
+    return AESCipher(_sk, parameters);
   }
 
   @override