Removed fixed dependencies

packages/crypto/lib/src/hmac.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'digest.dart';
+import 'digest_sink.dart';
+import 'hash.dart';
+
+/// An implementation of [keyed-hash method authentication codes][rfc].
+///
+/// [rfc]: https://tools.ietf.org/html/rfc2104
+///
+/// HMAC allows messages to be cryptographically authenticated using any
+/// iterated cryptographic hash function.
+class Hmac extends Converter<List<int>, Digest> {
+  /// The hash function used to compute the authentication digest.
+  final Hash _hash;
+
+  /// The secret key shared by the sender and the receiver.
+  final Uint8List _key;
+
+  /// Create an [Hmac] object from a [Hash] and a binary key.
+  ///
+  /// The key should be a secret shared between the sender and receiver of the
+  /// message.
+  Hmac(Hash hash, List<int> key)
+      : _hash = hash,
+        _key = new Uint8List(hash.blockSize) {
+    // Hash the key if it's longer than the block size of the hash.
+    if (key.length > _hash.blockSize) key = _hash.convert(key).bytes;
+
+    // If [key] is shorter than the block size, the rest of [_key] will be
+    // 0-padded.
+    _key.setRange(0, key.length, key);
+  }
+
+  @override
+  Digest convert(List<int> data) {
+    var innerSink = new DigestSink();
+    var outerSink = startChunkedConversion(innerSink);
+    outerSink.add(data);
+    outerSink.close();
+    return innerSink.value;
+  }
+
+  @override
+  ByteConversionSink startChunkedConversion(Sink<Digest> sink) =>
+      new _HmacSink(sink, _hash, _key);
+}
+
+/// The concrete implementation of the HMAC algorithm.
+class _HmacSink extends ByteConversionSink {
+  /// The sink for the outer hash computation.
+  final ByteConversionSink _outerSink;
+
+  /// The sink that [_innerSink]'s result will be added to when it's available.
+  final _innerResultSink = new DigestSink();
+
+  /// The sink for the inner hash computation.
+  ByteConversionSink _innerSink;
+
+  /// Whether [close] has been called.
+  bool _isClosed = false;
+
+  _HmacSink(Sink<Digest> sink, Hash hash, List<int> key)
+      : _outerSink = hash.startChunkedConversion(sink) {
+    _innerSink = hash.startChunkedConversion(_innerResultSink);
+
+    // Compute outer padding.
+    var padding = new Uint8List(key.length);
+    for (var i = 0; i < padding.length; i++) {
+      padding[i] = 0x5c ^ key[i];
+    }
+    _outerSink.add(padding);
+
+    // Compute inner padding.
+    for (var i = 0; i < padding.length; i++) {
+      padding[i] = 0x36 ^ key[i];
+    }
+    _innerSink.add(padding);
+  }
+
+  @override
+  void add(List<int> data) {
+    if (_isClosed) throw new StateError("HMAC is closed");
+    _innerSink.add(data);
+  }
+
+  @override
+  void addSlice(List<int> data, int start, int end, bool isLast) {
+    if (_isClosed) throw new StateError("HMAC is closed");
+    _innerSink.addSlice(data, start, end, isLast);
+  }
+
+  @override
+  void close() {
+    if (_isClosed) return;
+    _isClosed = true;
+
+    _innerSink.close();
+    _outerSink.add(_innerResultSink.value.bytes);
+    _outerSink.close();
+  }
+}