diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 000000000..a7592500e
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,4 @@
+## 2024-03-01 - [Fast String Concatenation and Secure Random]
+
+**Learning:** String concatenation using `+=` inside loops is very slow for large iterations (O(N^2)). Using `StringBuffer` or allocating a `List<int>` and using `String.fromCharCodes` is significantly faster (O(N)). Additionally, `Random.secure()` has a slight performance overhead but is essential for IDs to prevent predictability. Caching `Random.secure()` instances avoids initialization overhead.
+**Action:** Replace `+=` string concatenation with `String.fromCharCodes` inside random string generators. Cache `Random.secure()` to save instantiation time.
diff --git a/lib/abgabe/abgabe_client_lib/lib/src/models/auto_id_generator.dart b/lib/abgabe/abgabe_client_lib/lib/src/models/auto_id_generator.dart
index 86c44fb09..ce3df0a63 100644
--- a/lib/abgabe/abgabe_client_lib/lib/src/models/auto_id_generator.dart
+++ b/lib/abgabe/abgabe_client_lib/lib/src/models/auto_id_generator.dart
@@ -16,17 +16,16 @@ class AutoIdGenerator {
   static const String alphabet =
       'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
 
-  static final Random _random = Random();
+  static final Random _secureRandom = Random.secure();
+  static final _alphabetCodeUnits = alphabet.codeUnits;
 
   /// Automatically Generates a random new Id
   static String autoId() {
-    final stringBuffer = StringBuffer();
-    const maxRandom = alphabet.length;
-
-    for (var i = 0; i < idLength; ++i) {
-      stringBuffer.write(alphabet[_random.nextInt(maxRandom)]);
-    }
-
-    return stringBuffer.toString();
+    final codes = List<int>.generate(
+      idLength,
+      (_) =>
+          _alphabetCodeUnits[_secureRandom.nextInt(_alphabetCodeUnits.length)],
+    );
+    return String.fromCharCodes(codes);
   }
 }
diff --git a/lib/common_domain_models/lib/src/ids/src/id.dart b/lib/common_domain_models/lib/src/ids/src/id.dart
index 022a684c5..e08cb94ad 100644
--- a/lib/common_domain_models/lib/src/ids/src/id.dart
+++ b/lib/common_domain_models/lib/src/ids/src/id.dart
@@ -8,6 +8,10 @@
 
 import 'dart:math';
 
+final _secureRandom = Random.secure();
+const _chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
+final _charCodes = _chars.codeUnits;
+
 class Id {
   final String value;
 
@@ -21,15 +25,12 @@ class Id {
   /// Generates a new random [Id] with the given [length] using characters
   /// from a-z, A-Z and 0-9.
   static Id generate({int length = 20, Random? random}) {
-    random ??= Random();
-    const chars =
-        'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
-    final id =
-        List.generate(
-          length,
-          (index) => chars[random!.nextInt(chars.length)],
-        ).join();
-    return Id(id);
+    final rand = random ?? _secureRandom;
+    final codes = List<int>.generate(
+      length,
+      (_) => _charCodes[rand.nextInt(_charCodes.length)],
+    );
+    return Id(String.fromCharCodes(codes));
   }
 
   @override
diff --git a/lib/sharezone_utils/lib/src/random_string/random_string.dart b/lib/sharezone_utils/lib/src/random_string/random_string.dart
index 2322868a4..1ebd9aca2 100644
--- a/lib/sharezone_utils/lib/src/random_string/random_string.dart
+++ b/lib/sharezone_utils/lib/src/random_string/random_string.dart
@@ -8,22 +8,23 @@
 
 import 'dart:math';
 
+final _secureRandom = Random.secure();
+const _idChars =
+    'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+final _idCharCodes = _idChars.codeUnits;
+
 String randomString(int length) {
-  var rand = Random();
   var codeUnits = List.generate(length, (index) {
-    return rand.nextInt(33) + 89;
+    return _secureRandom.nextInt(33) + 89;
   });
 
   return String.fromCharCodes(codeUnits);
 }
 
 String randomIDString(int length) {
-  var rand = Random();
-  const chars =
-      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
-  String result = "";
-  for (var i = 0; i < length; i++) {
-    result += chars[rand.nextInt(chars.length)];
-  }
-  return result;
+  final codes = List<int>.generate(
+    length,
+    (_) => _idCharCodes[_secureRandom.nextInt(_idCharCodes.length)],
+  );
+  return String.fromCharCodes(codes);
 }