diff --git a/lib/src/helpers.dart b/lib/src/helpers.dart
index e720cbe6..bc6af757 100644
--- a/lib/src/helpers.dart
+++ b/lib/src/helpers.dart
@@ -7,6 +7,7 @@ import 'dart:math';
 import 'dart:typed_data';
 
 import 'package:pointycastle/api.dart' as pc;
+import 'package:pointycastle/api.dart';
 
 import 'crypto/math/byte_ext.dart';
 import 'crypto/math/int_ext.dart';
@@ -104,4 +105,13 @@ class Helper {
     } while (k.compareTo(min) <= 0 || k.compareTo(max) >= 0);
     return k;
   }
+
+  static Uint8List pad(Uint8List bytes, int blockSize) {
+    final padLength = blockSize - (bytes.length % blockSize);
+
+    final padded = Uint8List(bytes.length + padLength)..setAll(0, bytes);
+    Padding('PKCS7').addPadding(padded, bytes.length);
+
+    return padded;
+  }
 }
diff --git a/lib/src/packet/secret_key.dart b/lib/src/packet/secret_key.dart
index 0fe248e6..7d9ef173 100644
--- a/lib/src/packet/secret_key.dart
+++ b/lib/src/packet/secret_key.dart
@@ -227,10 +227,15 @@ class SecretKeyPacket extends ContainedPacket implements KeyPacket {
       );
 
       final clearText = secretParams!.encode();
-      final cipherText = cipher.process(Uint8List.fromList([
-        ...clearText,
-        ...Helper.hashDigest(clearText, HashAlgorithm.sha1),
-      ]));
+      final cipherText = cipher.process(
+        Helper.pad(
+          Uint8List.fromList([
+            ...clearText,
+            ...Helper.hashDigest(clearText, HashAlgorithm.sha1),
+          ]),
+          symmetric.blockSize,
+        ),
+      );
 
       return SecretKeyPacket(
         publicKey,
@@ -255,10 +260,8 @@ class SecretKeyPacket extends ContainedPacket implements KeyPacket {
               symmetric.keySizeInByte,
             ) ??
             Uint8List(symmetric.keySizeInByte);
-        final blockSize = symmetric.blockSize;
-        final padding = Padding('PKCS7');
         final cipher = PaddedBlockCipherImpl(
-          padding,
+          Padding('PKCS7'),
           symmetric.cfbCipherEngine,
         );
         cipher.init(
@@ -266,17 +269,15 @@ class SecretKeyPacket extends ContainedPacket implements KeyPacket {
           PaddedBlockCipherParameters(
             ParametersWithIV(
               KeyParameter(key),
-              iv ?? Uint8List(blockSize),
+              iv ?? Uint8List(symmetric.blockSize),
             ),
             null,
           ),
         );
 
-        final padLength = blockSize - (keyData.length % blockSize);
-        final padded = Uint8List(keyData.length + padLength)..setAll(0, keyData);
-        padding.addPadding(padded, keyData.length);
-
-        final clearTextWithHash = cipher.process(padded);
+        final clearTextWithHash = cipher.process(
+          Helper.pad(keyData, symmetric.blockSize),
+        );
         clearText = clearTextWithHash.sublist(
           0,
           clearTextWithHash.length - HashAlgorithm.sha1.digestSize,
diff --git a/lib/src/packet/sym_encrypted_data.dart b/lib/src/packet/sym_encrypted_data.dart
index ed6c3b18..7f6984a1 100644
--- a/lib/src/packet/sym_encrypted_data.dart
+++ b/lib/src/packet/sym_encrypted_data.dart
@@ -65,7 +65,12 @@ class SymEncryptedDataPacket extends ContainedPacket {
     return SymEncryptedDataPacket(
       Uint8List.fromList([
         ...prefix,
-        ...cipher.process(packets.encode()),
+        ...cipher.process(
+          Helper.pad(
+            packets.encode(),
+            symmetric.blockSize,
+          ),
+        ),
       ]),
       packets: packets,
     );
@@ -101,9 +106,8 @@ class SymEncryptedDataPacket extends ContainedPacket {
       throw StateError('Message is not authenticated.');
     }
     final blockSize = symmetric.blockSize;
-    final padding = Padding('PKCS7');
     final cipher = PaddedBlockCipherImpl(
-      padding,
+      Padding('PKCS7'),
       symmetric.cfbCipherEngine,
     );
     cipher.init(
@@ -117,15 +121,15 @@ class SymEncryptedDataPacket extends ContainedPacket {
       ),
     );
 
-    final data = encrypted.sublist(blockSize + 2);
-    final padLength = blockSize - (data.length % blockSize);
-    final padded = Uint8List(data.length + padLength)..setAll(0, data);
-    padding.addPadding(padded, data.length);
-
     return SymEncryptedDataPacket(
       encrypted,
       packets: PacketList.packetDecode(
-        cipher.process(padded),
+        cipher.process(
+          Helper.pad(
+            encrypted.sublist(blockSize + 2),
+            blockSize,
+          ),
+        ),
       ),
     );
   }
diff --git a/lib/src/packet/sym_encrypted_integrity_protected_data.dart b/lib/src/packet/sym_encrypted_integrity_protected_data.dart
index acb80fe6..251561bd 100644
--- a/lib/src/packet/sym_encrypted_integrity_protected_data.dart
+++ b/lib/src/packet/sym_encrypted_integrity_protected_data.dart
@@ -80,7 +80,7 @@ class SymEncryptedIntegrityProtectedDataPacket extends ContainedPacket {
     );
 
     return SymEncryptedIntegrityProtectedDataPacket(
-      cipher.process(plainText),
+      cipher.process(Helper.pad(plainText, symmetric.blockSize)),
       packets: packets,
     );
   }
@@ -110,10 +110,8 @@ class SymEncryptedIntegrityProtectedDataPacket extends ContainedPacket {
     final Uint8List key, {
     final SymmetricAlgorithm symmetric = SymmetricAlgorithm.aes128,
   }) async {
-    final blockSize = symmetric.blockSize;
-    final padding = Padding('PKCS7');
     final cipher = PaddedBlockCipherImpl(
-      padding,
+      Padding('PKCS7'),
       symmetric.cfbCipherEngine,
     );
     cipher.init(
@@ -121,17 +119,15 @@ class SymEncryptedIntegrityProtectedDataPacket extends ContainedPacket {
       PaddedBlockCipherParameters(
         ParametersWithIV(
           KeyParameter(key),
-          Uint8List(blockSize),
+          Uint8List(symmetric.blockSize),
         ),
         null,
       ),
     );
 
-    final padLength = blockSize - (encrypted.length % blockSize);
-    final padded = Uint8List(encrypted.length + padLength)..setAll(0, encrypted);
-    padding.addPadding(padded, encrypted.length);
-
-    final decrypted = cipher.process(padded);
+    final decrypted = cipher.process(
+      Helper.pad(encrypted, symmetric.blockSize),
+    );
     final realHash = decrypted.sublist(
       decrypted.length - HashAlgorithm.sha1.digestSize,
     );
diff --git a/lib/src/packet/sym_encrypted_session_key.dart b/lib/src/packet/sym_encrypted_session_key.dart
index 43d2af2b..a8e814e6 100644
--- a/lib/src/packet/sym_encrypted_session_key.dart
+++ b/lib/src/packet/sym_encrypted_session_key.dart
@@ -156,7 +156,9 @@ class SymEncryptedSessionKeyPacket extends ContainedPacket {
           ),
         );
         iv = Uint8List(0);
-        encrypted = cipher.process(sessionKey.encode());
+        encrypted = cipher.process(
+          Helper.pad(sessionKey.encode(), symmetric.blockSize),
+        );
       }
     } else {
       iv = Uint8List(0);
@@ -196,10 +198,8 @@ class SymEncryptedSessionKeyPacket extends ContainedPacket {
           final decrypted = cipher.decrypt(encrypted, iv, adata);
           sessionKey = SessionKey(decrypted, symmetric);
         } else {
-          final blockSize = symmetric.blockSize;
-          final padding = Padding('PKCS7');
           final cipher = PaddedBlockCipherImpl(
-            padding,
+            Padding('PKCS7'),
             symmetric.cfbCipherEngine,
           );
           cipher.init(
@@ -207,17 +207,15 @@ class SymEncryptedSessionKeyPacket extends ContainedPacket {
             PaddedBlockCipherParameters(
               ParametersWithIV(
                 KeyParameter(key),
-                Uint8List(blockSize),
+                Uint8List(symmetric.blockSize),
               ),
               null,
             ),
           );
 
-          final padLength = blockSize - (encrypted.length % blockSize);
-          final padded = Uint8List(encrypted.length + padLength)..setAll(0, encrypted);
-          padding.addPadding(padded, encrypted.length);
-
-          final decrypted = cipher.process(padded);
+          final decrypted = cipher.process(
+            Helper.pad(encrypted, symmetric.blockSize),
+          );
           final sessionKeySymmetric = SymmetricAlgorithm.values.firstWhere(
             (algo) => algo.value == decrypted[0],
           );