diff --git a/lib/kdbx.dart b/lib/kdbx.dart
index 5e82379..8b7b849 100644
--- a/lib/kdbx.dart
+++ b/lib/kdbx.dart
@@ -1,7 +1,7 @@
 /// dart library for reading keepass file format (kdbx).
 library kdbx;
 
-export 'src/crypto/protected_value.dart' show ProtectedValue, StringValue;
+export 'src/crypto/protected_value.dart' show ProtectedValue, StringValue, PlainValue;
 export 'src/kdbx_entry.dart';
 export 'src/kdbx_format.dart';
 export 'src/kdbx_header.dart'
diff --git a/lib/src/kdbx_entry.dart b/lib/src/kdbx_entry.dart
index 3635440..8ac97a5 100644
--- a/lib/src/kdbx_entry.dart
+++ b/lib/src/kdbx_entry.dart
@@ -3,6 +3,7 @@ import 'package:kdbx/src/kdbx_consts.dart';
 import 'package:kdbx/src/kdbx_format.dart';
 import 'package:kdbx/src/kdbx_group.dart';
 import 'package:kdbx/src/kdbx_object.dart';
+import 'package:kdbx/src/kdbx_xml.dart';
 import 'package:xml/xml.dart';
 
 /// Represents a case insensitive (but case preserving) key.
@@ -21,15 +22,16 @@ class KdbxKey {
 }
 
 class KdbxEntry extends KdbxObject {
-  KdbxEntry.create(this.parent) : super.create('Entry') {
+  KdbxEntry.create(KdbxFile file, this.parent) : super.create(file, 'Entry') {
     icon.set(KdbxIcon.Key);
   }
 
   KdbxEntry.read(this.parent, XmlElement node) : super.read(node) {
-    _strings.addEntries(node.findElements('String').map((el) {
-      final key = KdbxKey(el.findElements('Key').single.text);
-      final valueNode = el.findElements('Value').single;
-      if (valueNode.getAttribute('Protected')?.toLowerCase() == 'true') {
+    _strings.addEntries(node.findElements(KdbxXml.NODE_STRING).map((el) {
+      final key = KdbxKey(el.findElements(KdbxXml.NODE_KEY).single.text);
+      final valueNode = el.findElements(KdbxXml.NODE_VALUE).single;
+      if (valueNode.getAttribute(KdbxXml.ATTR_PROTECTED)?.toLowerCase() ==
+          'true') {
         return MapEntry(key, KdbxFile.protectedValueForNode(valueNode));
       } else {
         return MapEntry(key, PlainValue(valueNode.text));
@@ -37,22 +39,52 @@ class KdbxEntry extends KdbxObject {
     }));
   }
 
+  List<KdbxEntry> _history;
+
+  List<KdbxEntry> get history =>
+      _history ??
+      (() {
+        return _historyElement
+            .findElements('Entry')
+            .map((entry) => KdbxEntry.read(parent, entry))
+            .toList();
+      })();
+
+  XmlElement get _historyElement => node
+          .findElements(KdbxXml.NODE_HISTORY)
+          .singleWhere((_) => true, orElse: () {
+        final el = XmlElement(XmlName(KdbxXml.NODE_HISTORY));
+        node.children.add(el);
+        return el;
+      });
+
+  @override
+  set isDirty(bool newDirty) {
+    if (!isDirty && newDirty) {
+      final history = _historyElement;
+      history.children.add(toXml());
+    }
+    super.isDirty = newDirty;
+  }
+
   @override
   XmlElement toXml() {
     final el = super.toXml();
-    el.children.removeWhere((e) => e is XmlElement && e.name.local == 'String');
+    el.children.removeWhere(
+        (e) => e is XmlElement && e.name.local == KdbxXml.NODE_STRING);
     el.children.addAll(stringEntries.map((stringEntry) {
-      final value = XmlElement(XmlName('Value'));
+      final value = XmlElement(XmlName(KdbxXml.NODE_VALUE));
       if (stringEntry.value is ProtectedValue) {
-        value.attributes.add(XmlAttribute(XmlName('Protected'), 'true'));
+        value.attributes
+            .add(XmlAttribute(XmlName(KdbxXml.ATTR_PROTECTED), 'true'));
         KdbxFile.setProtectedValueForNode(
             value, stringEntry.value as ProtectedValue);
       } else {
         value.children.add(XmlText(stringEntry.value.getText()));
       }
-      return XmlElement(XmlName('String'))
+      return XmlElement(XmlName(KdbxXml.NODE_STRING))
         ..children.addAll([
-          XmlElement(XmlName('Key'))
+          XmlElement(XmlName(KdbxXml.ATTR_PROTECTED))
             ..children.add(XmlText(stringEntry.key.key)),
           value,
         ]);
@@ -65,11 +97,13 @@ class KdbxEntry extends KdbxObject {
 
 //  Map<KdbxKey, StringValue> get strings => UnmodifiableMapView(_strings);
 
-  Iterable<MapEntry<KdbxKey, StringValue>> get stringEntries => _strings.entries;
+  Iterable<MapEntry<KdbxKey, StringValue>> get stringEntries =>
+      _strings.entries;
 
   StringValue getString(KdbxKey key) => _strings[key];
 
   void setString(KdbxKey key, StringValue value) {
+    isDirty = true;
     _strings[key] = value;
   }
 
diff --git a/lib/src/kdbx_format.dart b/lib/src/kdbx_format.dart
index 20b2c29..a86f83e 100644
--- a/lib/src/kdbx_format.dart
+++ b/lib/src/kdbx_format.dart
@@ -6,7 +6,6 @@ import 'package:convert/convert.dart' as convert;
 import 'package:crypto/crypto.dart' as crypto;
 import 'package:kdbx/src/crypto/protected_salt_generator.dart';
 import 'package:kdbx/src/crypto/protected_value.dart';
-import 'package:kdbx/src/internal/async_utils.dart';
 import 'package:kdbx/src/internal/byte_utils.dart';
 import 'package:kdbx/src/internal/crypto_utils.dart';
 import 'package:kdbx/src/kdbx_group.dart';
@@ -36,7 +35,11 @@ class Credentials {
 }
 
 class KdbxFile {
-  KdbxFile(this.credentials, this.header, this.body);
+  KdbxFile(this.credentials, this.header, this.body) {
+    for (final obj in _allObjects) {
+      obj.file = this;
+    }
+  }
 
   static final protectedValues = Expando<ProtectedValue>();
 
@@ -52,6 +55,7 @@ class KdbxFile {
   final Credentials credentials;
   final KdbxHeader header;
   final KdbxBody body;
+  final Set<KdbxObject> dirtyObjects = {};
 
   Uint8List save() {
     assert(header.versionMajor == 3);
@@ -68,6 +72,7 @@ class KdbxFile {
         (crypto.sha256.convert(writer.output.toBytes()).bytes as Uint8List)
             .buffer);
     body.writeV3(writer, this, gen);
+    dirtyObjects.clear();
     return output.toBytes();
   }
 
@@ -76,6 +81,10 @@ class KdbxFile {
       .cast<KdbxObject>()
       .followedBy(body.rootGroup.getAllEntries());
 
+  void dirtyObject(KdbxObject kdbxObject) {
+    dirtyObjects.add(kdbxObject);
+  }
+
 //  void _subscribeToChildren() {
 //    final allObjects = _allObjects;
 //    for (final obj in allObjects) {
diff --git a/lib/src/kdbx_group.dart b/lib/src/kdbx_group.dart
index 3a4d7f1..4500a0e 100644
--- a/lib/src/kdbx_group.dart
+++ b/lib/src/kdbx_group.dart
@@ -1,3 +1,4 @@
+import 'package:kdbx/kdbx.dart';
 import 'package:kdbx/src/internal/async_utils.dart';
 import 'package:kdbx/src/kdbx_consts.dart';
 import 'package:kdbx/src/kdbx_entry.dart';
@@ -9,7 +10,7 @@ import 'kdbx_object.dart';
 
 class KdbxGroup extends KdbxObject {
   KdbxGroup.create({@required this.parent, @required String name})
-      : super.create('Group') {
+      : super.create(parent?.file, 'Group') {
     this.name.set(name);
     icon.set(KdbxIcon.Folder);
     expanded.set(true);
diff --git a/lib/src/kdbx_object.dart b/lib/src/kdbx_object.dart
index 78ea8af..8baa369 100644
--- a/lib/src/kdbx_object.dart
+++ b/lib/src/kdbx_object.dart
@@ -2,6 +2,7 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
 
+import 'package:kdbx/src/kdbx_format.dart';
 import 'package:kdbx/src/kdbx_times.dart';
 import 'package:kdbx/src/kdbx_xml.dart';
 import 'package:meta/meta.dart';
@@ -30,7 +31,7 @@ mixin Changeable<T> {
 
 abstract class KdbxNode with Changeable<KdbxNode> {
   KdbxNode.create(String nodeName) : node = XmlElement(XmlName(nodeName)) {
-    isDirty = true;
+    _isDirty = true;
   }
 
   KdbxNode.read(this.node);
@@ -48,13 +49,16 @@ abstract class KdbxNode with Changeable<KdbxNode> {
 }
 
 abstract class KdbxObject extends KdbxNode {
-  KdbxObject.create(String nodeName)
+  KdbxObject.create(this.file, String nodeName)
       : times = KdbxTimes.create(), super.create(nodeName) {
     _uuid.set(KdbxUuid.random());
   }
 
   KdbxObject.read(XmlElement node) : times = KdbxTimes.read(node.findElements('Times').single),super.read(node);
 
+  /// the file this object is part of. will be set AFTER loading, etc.
+  KdbxFile file;
+
   final KdbxTimes times;
 
   KdbxUuid get uuid => _uuid.get();
@@ -65,7 +69,10 @@ abstract class KdbxObject extends KdbxNode {
   @override
   set isDirty(bool dirty) {
     super.isDirty = dirty;
-    times.modifiedNow();
+    if (dirty) {
+      times.modifiedNow();
+      file.dirtyObject(this);
+    }
   }
 
   @override
diff --git a/lib/src/kdbx_xml.dart b/lib/src/kdbx_xml.dart
index 5144044..f312e96 100644
--- a/lib/src/kdbx_xml.dart
+++ b/lib/src/kdbx_xml.dart
@@ -6,6 +6,14 @@ import 'package:kdbx/src/kdbx_consts.dart';
 import 'package:meta/meta.dart';
 import 'package:xml/xml.dart';
 
+class KdbxXml {
+  static const NODE_STRING = 'String';
+  static const NODE_KEY = 'Key';
+  static const NODE_VALUE = 'Value';
+  static const ATTR_PROTECTED = 'Protected';
+  static const NODE_HISTORY = 'History';
+}
+
 abstract class KdbxSubNode<T> {
   KdbxSubNode(this.node, this.name);
 
diff --git a/test/kdbx_test.dart b/test/kdbx_test.dart
index 42b83a2..70f5cc6 100644
--- a/test/kdbx_test.dart
+++ b/test/kdbx_test.dart
@@ -43,7 +43,7 @@ void main() {
     test('Create Entry', () {
       final kdbx = KdbxFormat.create(Credentials(ProtectedValue.fromString('FooBar')), 'CreateTest');
       final rootGroup = kdbx.body.rootGroup;
-      final entry = KdbxEntry.create(rootGroup);
+      final entry = KdbxEntry.create(kdbx, rootGroup);
       rootGroup.addEntry(entry);
       entry.setString(KdbxKey('Password'), ProtectedValue.fromString('LoremIpsum'));
       print(kdbx.body.generateXml(FakeProtectedSaltGenerator()).toXmlString(pretty: true));
@@ -56,7 +56,7 @@ void main() {
       final Uint8List saved = (() {
         final kdbx = KdbxFormat.create(credentials, 'CreateTest');
         final rootGroup = kdbx.body.rootGroup;
-        final entry = KdbxEntry.create(rootGroup);
+        final entry = KdbxEntry.create(kdbx, rootGroup);
         rootGroup.addEntry(entry);
         entry.setString(
             KdbxKey('Password'), ProtectedValue.fromString('LoremIpsum'));