log more debugging info when unable to decode protected value.

lib/src/internal/extension_utils.dart

@@ -21,6 +21,14 @@ extension XmlElementExt on xml.XmlElement {
     return findElements(nodeName).single.text;
   }
 
+  Iterable<xml.XmlElement> breadcrumbs() {
+    final ret = parentElement?.let((p) => p.breadcrumbs()) ?? [];
+    return [this].followedBy(ret);
+  }
+
+  String breadcrumbsNames() =>
+      breadcrumbs().map((e) => e.name.local).join(' / ');
+
   /// If an element child with the given name already exists,
   /// it will be removed and the given element will be added.
   /// otherwise it will be only added.

lib/src/kdbx_format.dart

@@ -773,11 +773,27 @@ class KdbxFormat {
     for (final el in document
         .findAllElements(KdbxXml.NODE_VALUE)
         .where((el) => el.getAttributeBool(KdbxXml.ATTR_PROTECTED))) {
+      try {
         final pw = gen.decryptBase64(el.text.trim());
         if (pw == null) {
           continue;
         }
         KdbxFile.protectedValues[el] = ProtectedValue.fromString(pw);
+      } catch (e, stackTrace) {
+        final stringKey =
+            el.parentElement.singleElement(KdbxXml.NODE_KEY)?.text;
+        final uuid = el.parentElement?.parentElement
+            ?.singleElement(KdbxXml.NODE_UUID)
+            ?.text;
+        _logger.severe(
+            'Error while decoding protected value in '
+            '{${el.breadcrumbsNames()}} of key'
+            ' {$stringKey} of entry {$uuid}.',
+            e,
+            stackTrace);
+
+        rethrow;
+      }
     }
 
     final keePassFile = document.findElements('KeePassFile').single;