Removed fixed dependencies

packages/crypto/lib/src/digest.dart

+// Copyright (c) 2015, 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 'package:collection/collection.dart';
+import 'package:convert/convert.dart';
+
+/// A message digest as computed by a `Hash` or `HMAC` function.
+class Digest {
+  /// The message digest as an array of bytes.
+  final List<int> bytes;
+
+  Digest(this.bytes);
+
+  /// Returns whether this is equal to another digest.
+  ///
+  /// This should be used instead of manual comparisons to avoid leaking
+  /// information via timing.
+  @override
+  bool operator ==(Object other) =>
+      other is Digest && const ListEquality().equals(bytes, other.bytes);
+
+  @override
+  int get hashCode => const ListEquality().hash(bytes);
+
+  /// The message digest as a string of hexadecimal digits.
+  @override
+  String toString() => hex.encode(bytes);
+}