diff --git a/lib/src/common/config.dart b/lib/src/common/config.dart
index cb1742a8..192b0861 100644
--- a/lib/src/common/config.dart
+++ b/lib/src/common/config.dart
@@ -29,7 +29,7 @@ final class Config {
 
   static HashAlgorithm preferredHash = HashAlgorithm.sha256;
 
-  static SymmetricAlgorithm preferredSymmetric = SymmetricAlgorithm.aes128;
+  static SymmetricAlgorithm preferredSymmetric = SymmetricAlgorithm.aes256;
 
   static CompressionAlgorithm preferredCompression =
       CompressionAlgorithm.uncompressed;
diff --git a/lib/src/cryptor/aead/eax.dart b/lib/src/cryptor/aead/eax.dart
index 0c0c6164..afd3259a 100644
--- a/lib/src/cryptor/aead/eax.dart
+++ b/lib/src/cryptor/aead/eax.dart
@@ -5,7 +5,6 @@
 library;
 
 import 'dart:typed_data';
-
 import 'package:pointycastle/export.dart';
 
 import '../../enum/symmetric_algorithm.dart';
diff --git a/lib/src/cryptor/aead/gcm.dart b/lib/src/cryptor/aead/gcm.dart
index 81211ed9..a91c520b 100644
--- a/lib/src/cryptor/aead/gcm.dart
+++ b/lib/src/cryptor/aead/gcm.dart
@@ -5,7 +5,6 @@
 library;
 
 import 'dart:typed_data';
-
 import 'package:pointycastle/export.dart';
 
 import '../../enum/symmetric_algorithm.dart';
diff --git a/lib/src/cryptor/symmetric/buffered_cipher.dart b/lib/src/cryptor/symmetric/buffered_cipher.dart
index 0acd0709..6b8fc3f0 100644
--- a/lib/src/cryptor/symmetric/buffered_cipher.dart
+++ b/lib/src/cryptor/symmetric/buffered_cipher.dart
@@ -5,7 +5,6 @@
 library;
 
 import 'dart:typed_data';
-
 import 'package:pointycastle/api.dart';
 
 /// Buffered cipher.
diff --git a/lib/src/cryptor/symmetric/camellia.dart b/lib/src/cryptor/symmetric/camellia.dart
index 9eee7101..6d5bd99b 100644
--- a/lib/src/cryptor/symmetric/camellia.dart
+++ b/lib/src/cryptor/symmetric/camellia.dart
@@ -7,8 +7,8 @@ library;
 import 'dart:typed_data';
 import 'package:pointycastle/api.dart';
 
-import 'base_engine.dart';
 import '../../common/extensions.dart';
+import 'base_engine.dart';
 
 /// Camellia - based on RFC 3713.
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
diff --git a/lib/src/cryptor/symmetric/cast5.dart b/lib/src/cryptor/symmetric/cast5.dart
index 57189a62..953fce34 100644
--- a/lib/src/cryptor/symmetric/cast5.dart
+++ b/lib/src/cryptor/symmetric/cast5.dart
@@ -7,8 +7,8 @@ library;
 import 'dart:typed_data';
 import 'package:pointycastle/api.dart';
 
-import 'base_engine.dart';
 import '../../common/extensions.dart';
+import 'base_engine.dart';
 
 /// A class that provides CAST key encryption operations, such as encoding data and generating keys.
 /// All the algorithms herein are from the Internet RFC's
diff --git a/lib/src/cryptor/symmetric/idea.dart b/lib/src/cryptor/symmetric/idea.dart
index 78585641..d5f963ea 100644
--- a/lib/src/cryptor/symmetric/idea.dart
+++ b/lib/src/cryptor/symmetric/idea.dart
@@ -7,8 +7,8 @@ library;
 import 'dart:typed_data';
 import 'package:pointycastle/api.dart';
 
-import 'base_engine.dart';
 import '../../common/extensions.dart';
+import 'base_engine.dart';
 
 /// A class that provides a basic International Data Encryption Algorithm (IDEA) engine.
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
diff --git a/lib/src/cryptor/symmetric/twofish.dart b/lib/src/cryptor/symmetric/twofish.dart
index 2cc716b3..1eb8750a 100644
--- a/lib/src/cryptor/symmetric/twofish.dart
+++ b/lib/src/cryptor/symmetric/twofish.dart
@@ -7,8 +7,8 @@ library;
 import 'dart:typed_data';
 import 'package:pointycastle/api.dart';
 
-import 'base_engine.dart';
 import '../../common/extensions.dart';
+import 'base_engine.dart';
 
 /// A class that provides Twofish encryption operations.
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
diff --git a/lib/src/enum/signature_type.dart b/lib/src/enum/signature_type.dart
index e28da968..c000e16c 100644
--- a/lib/src/enum/signature_type.dart
+++ b/lib/src/enum/signature_type.dart
@@ -6,14 +6,14 @@ library;
 
 export 'aead_algorithm.dart';
 export 'compression_algorithm.dart';
+export 'hash_algorithm.dart';
+export 'key_algorithm.dart';
 export 'key_flag.dart';
 export 'key_version.dart';
 export 'literal_format.dart';
+export 'signature_subpacket_type.dart';
 export 'support_feature.dart';
 export 'symmetric_algorithm.dart';
-export 'hash_algorithm.dart';
-export 'key_algorithm.dart';
-export 'signature_subpacket_type.dart';
 
 ///Signature types enum
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
diff --git a/lib/src/message/cleartext_message.dart b/lib/src/message/cleartext_message.dart
index 3f5eb722..82deef4d 100644
--- a/lib/src/message/cleartext_message.dart
+++ b/lib/src/message/cleartext_message.dart
@@ -5,13 +5,13 @@
 library;
 
 import '../common/helpers.dart';
-import '../message/signature.dart';
-import '../message/signed_message.dart';
 import '../packet/base_packet.dart';
 import '../type/cleartext_message.dart';
 import '../type/key.dart';
 import '../type/notation_data.dart';
 import '../type/signature.dart';
+import 'signature.dart';
+import 'signed_message.dart';
 
 /// Cleartext message class that represents an OpenPGP cleartext message.
 /// See RFC 9580, section 7.
diff --git a/lib/src/message/encrypted_message.dart b/lib/src/message/encrypted_message.dart
index ad104444..104c9298 100644
--- a/lib/src/message/encrypted_message.dart
+++ b/lib/src/message/encrypted_message.dart
@@ -7,13 +7,13 @@ library;
 import '../common/armor.dart';
 import '../common/helpers.dart';
 import '../enum/armor_type.dart';
-import '../message/base_message.dart';
 import '../packet/base_packet.dart';
 import '../type/encrypted_data_packet.dart';
 import '../type/encrypted_message.dart';
 import '../type/packet_list.dart';
 import '../type/private_key.dart';
 import '../type/session_key.dart';
+import 'base_message.dart';
 
 /// OpenPGP encrypted message class
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
diff --git a/lib/src/message/literal_message.dart b/lib/src/message/literal_message.dart
index 5ac61d74..7cccf0f3 100644
--- a/lib/src/message/literal_message.dart
+++ b/lib/src/message/literal_message.dart
@@ -13,7 +13,6 @@ import '../enum/aead_algorithm.dart';
 import '../enum/armor_type.dart';
 import '../enum/compression_algorithm.dart';
 import '../enum/symmetric_algorithm.dart';
-import '../message/base_message.dart';
 import '../packet/base_packet.dart';
 import '../packet/key/session_key.dart';
 import '../type/key.dart';
@@ -22,6 +21,7 @@ import '../type/literal_message.dart';
 import '../type/packet_list.dart';
 import '../type/session_key.dart';
 import '../type/signature_packet.dart';
+import 'base_message.dart';
 
 /// OpenPGP literal message class
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
@@ -59,7 +59,7 @@ final class LiteralMessage extends BaseMessage
   /// Taking the algorithm preferences of the passed encryption keys, if any.
   static SessionKeyInterface generateSessionKey(
     final Iterable<KeyInterface> encryptionKeys, [
-    final SymmetricAlgorithm defaultSymmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm defaultSymmetric = SymmetricAlgorithm.aes256,
   ]) {
     final SymmetricAlgorithm symmetric;
     if (encryptionKeys.isNotEmpty) {
@@ -163,7 +163,7 @@ final class LiteralMessage extends BaseMessage
   encrypt({
     final Iterable<KeyInterface> encryptionKeys = const [],
     final Iterable<String> passwords = const [],
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
   }) {
     final sessionKey = generateSessionKey(
       encryptionKeys,
diff --git a/lib/src/message/signature.dart b/lib/src/message/signature.dart
index 82330d87..57fc733a 100644
--- a/lib/src/message/signature.dart
+++ b/lib/src/message/signature.dart
@@ -8,7 +8,6 @@ import '../common/armor.dart';
 import '../common/helpers.dart';
 import '../enum/armor_type.dart';
 import '../enum/hash_algorithm.dart';
-import '../message/verification.dart';
 import '../packet/base_packet.dart';
 import '../type/cleartext_message.dart';
 import '../type/key.dart';
@@ -16,6 +15,7 @@ import '../type/literal_data.dart';
 import '../type/signature.dart';
 import '../type/signature_packet.dart';
 import '../type/verification.dart';
+import 'verification.dart';
 
 /// Signature class
 /// Author Nguyen Van Nguyen <nguyennv1981@gmail.com>
diff --git a/lib/src/message/signed_message.dart b/lib/src/message/signed_message.dart
index e3cd8d9c..fd01f615 100644
--- a/lib/src/message/signed_message.dart
+++ b/lib/src/message/signed_message.dart
@@ -6,13 +6,13 @@ library;
 
 import '../common/armor.dart';
 import '../enum/armor_type.dart';
-import '../message/signature.dart';
 import '../packet/packet_list.dart';
 import '../type/key.dart';
 import '../type/signature.dart';
 import '../type/signature_packet.dart';
 import '../type/signed_cleartext_message.dart';
 import 'cleartext_message.dart';
+import 'signature.dart';
 
 /// Signed message class that represents an OpenPGP cleartext signed message.
 /// See RFC 9580, section 7.
diff --git a/lib/src/packet/aead_encrypted_data.dart b/lib/src/packet/aead_encrypted_data.dart
index 81bb0208..e5820b5a 100644
--- a/lib/src/packet/aead_encrypted_data.dart
+++ b/lib/src/packet/aead_encrypted_data.dart
@@ -81,7 +81,7 @@ final class AeadEncryptedDataPacket extends BasePacket
   factory AeadEncryptedDataPacket.encryptPackets(
     final Uint8List key,
     final PacketListInterface packets, {
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
     final AeadAlgorithm aead = AeadAlgorithm.ocb,
     final int chunkSize = 12,
   }) {
@@ -117,7 +117,7 @@ final class AeadEncryptedDataPacket extends BasePacket
   @override
   decrypt(
     final Uint8List key, [
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
   ]) {
     final length = encrypted.length;
     final data = encrypted.sublist(0, length - aead.tagLength);
@@ -147,7 +147,7 @@ final class AeadEncryptedDataPacket extends BasePacket
     final Uint8List key,
     final Uint8List data, {
     final Uint8List? finalChunk,
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
     final AeadAlgorithm aead = AeadAlgorithm.ocb,
     final chunkSizeByte = 0,
     final Uint8List? iv,
diff --git a/lib/src/packet/key/dsa_public_material.dart b/lib/src/packet/key/dsa_public_material.dart
index e1b99f13..565513bc 100644
--- a/lib/src/packet/key/dsa_public_material.dart
+++ b/lib/src/packet/key/dsa_public_material.dart
@@ -5,7 +5,6 @@
 library;
 
 import 'dart:typed_data';
-
 import 'package:pointycastle/export.dart';
 
 import '../../common/helpers.dart';
diff --git a/lib/src/packet/key/rsa_secret_material.dart b/lib/src/packet/key/rsa_secret_material.dart
index 94c103aa..0637c6df 100644
--- a/lib/src/packet/key/rsa_secret_material.dart
+++ b/lib/src/packet/key/rsa_secret_material.dart
@@ -5,7 +5,6 @@
 library;
 
 import 'dart:typed_data';
-
 import 'package:pointycastle/pointycastle.dart';
 
 import '../../common/helpers.dart';
diff --git a/lib/src/packet/signature.dart b/lib/src/packet/signature.dart
index b6728c55..294b8476 100644
--- a/lib/src/packet/signature.dart
+++ b/lib/src/packet/signature.dart
@@ -501,8 +501,8 @@ final class SignaturePacket extends BasePacket
         KeyFlag.certifyKeys.value | KeyFlag.signData.value,
       ),
       PreferredSymmetricAlgorithms(Uint8List.fromList([
-        SymmetricAlgorithm.aes128.value,
         SymmetricAlgorithm.aes256.value,
+        SymmetricAlgorithm.aes128.value,
       ])),
       PreferredAeadAlgorithms(Uint8List.fromList([
         AeadAlgorithm.ocb.value,
@@ -529,18 +529,18 @@ final class SignaturePacket extends BasePacket
     if (version == KeyVersion.v6.value) {
       subpackets.add(PreferredAeadCiphers(Uint8List.fromList([
         ...[
-          SymmetricAlgorithm.aes128.value,
+          SymmetricAlgorithm.aes256.value,
           AeadAlgorithm.ocb.value,
-          SymmetricAlgorithm.aes128.value,
+          SymmetricAlgorithm.aes256.value,
           AeadAlgorithm.gcm.value,
-          SymmetricAlgorithm.aes128.value,
-          AeadAlgorithm.eax.value,
         ],
         ...[
-          SymmetricAlgorithm.aes256.value,
+          SymmetricAlgorithm.aes128.value,
           AeadAlgorithm.ocb.value,
-          SymmetricAlgorithm.aes256.value,
+          SymmetricAlgorithm.aes128.value,
           AeadAlgorithm.gcm.value,
+          SymmetricAlgorithm.aes128.value,
+          AeadAlgorithm.eax.value,
         ],
       ])));
     }
diff --git a/lib/src/packet/sym_encrypted_data.dart b/lib/src/packet/sym_encrypted_data.dart
index cf3716cc..5426a891 100644
--- a/lib/src/packet/sym_encrypted_data.dart
+++ b/lib/src/packet/sym_encrypted_data.dart
@@ -70,7 +70,7 @@ final class SymEncryptedDataPacket extends BasePacket
   @override
   decrypt(
     final Uint8List key, [
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
   ]) {
     if (!Config.allowUnauthenticated) {
       throw AssertionError(
diff --git a/lib/src/packet/sym_encrypted_integrity_protected_data.dart b/lib/src/packet/sym_encrypted_integrity_protected_data.dart
index ae3effb0..598c8a6d 100644
--- a/lib/src/packet/sym_encrypted_integrity_protected_data.dart
+++ b/lib/src/packet/sym_encrypted_integrity_protected_data.dart
@@ -131,7 +131,7 @@ final class SymEncryptedIntegrityProtectedDataPacket extends BasePacket
   factory SymEncryptedIntegrityProtectedDataPacket.encryptPackets(
     final Uint8List key,
     final PacketListInterface packets, {
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
     final AeadAlgorithm? aead,
   }) {
     Helper.assertSymmetric(symmetric);
diff --git a/lib/src/packet/sym_encrypted_session_key.dart b/lib/src/packet/sym_encrypted_session_key.dart
index 61949739..cb9361b3 100644
--- a/lib/src/packet/sym_encrypted_session_key.dart
+++ b/lib/src/packet/sym_encrypted_session_key.dart
@@ -43,7 +43,7 @@ final class SymEncryptedSessionKeyPacket extends BasePacket {
     this.s2k,
     this.iv,
     this.encrypted, {
-    this.symmetric = SymmetricAlgorithm.aes128,
+    this.symmetric = SymmetricAlgorithm.aes256,
     this.aead,
     this.sessionKey,
   }) : super(PacketType.symEncryptedSessionKey) {
@@ -126,9 +126,9 @@ final class SymEncryptedSessionKeyPacket extends BasePacket {
 
   factory SymEncryptedSessionKeyPacket.encryptSessionKey(
     final String password, {
-    final SessionKeyInterface? sessionKey,
-    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
+    final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes256,
     final AeadAlgorithm? aead,
+    final SessionKeyInterface? sessionKey,
   }) {
     Helper.assertSymmetric(symmetric);
 
diff --git a/lib/src/packet/user_attribute.dart b/lib/src/packet/user_attribute.dart
index f0816df9..a8cbdec1 100644
--- a/lib/src/packet/user_attribute.dart
+++ b/lib/src/packet/user_attribute.dart
@@ -6,8 +6,8 @@ library;
 
 import 'dart:typed_data';
 
-import '../type/user_id_packet.dart';
 import '../common/extensions.dart';
+import '../type/user_id_packet.dart';
 import 'base_packet.dart';
 import 'image_user_attribute.dart';
 import 'subpacket_reader.dart';