diff --git a/src/Common/Config.php b/src/Common/Config.php
index 435de67..b7f33e9 100644
--- a/src/Common/Config.php
+++ b/src/Common/Config.php
@@ -88,6 +88,7 @@ public static function getPreferredHash(): HashAlgorithm
      */
     public static function setPreferredHash(HashAlgorithm $hash): void
     {
+        Helper::assertHash($hash);
         self::$preferredHash = $hash;
     }
 
@@ -110,6 +111,7 @@ public static function setPreferredSymmetric(
         SymmetricAlgorithm $symmetric
     ): void
     {
+        Helper::assertSymmetric($symmetric);
         self::$preferredSymmetric = $symmetric;
     }
 
@@ -175,6 +177,7 @@ public static function getS2kHash(): HashAlgorithm
      */
     public static function setS2kHash(HashAlgorithm $s2kHash): void
     {
+        Helper::assertHash($s2kHash);
         self::$s2kHash = $s2kHash;
     }
 
diff --git a/src/Common/Helper.php b/src/Common/Helper.php
index 6525cf3..9531254 100644
--- a/src/Common/Helper.php
+++ b/src/Common/Helper.php
@@ -9,6 +9,7 @@
 namespace OpenPGP\Common;
 
 use OpenPGP\Enum\{
+    HashAlgorithm,
     S2kType,
     SymmetricAlgorithm,
 };
@@ -209,4 +210,42 @@ public static function simpleLength(int $length): string
             return implode(["\xff", pack('N', $length)]);
         }
     }
+
+    /**
+     * Assert hash algorithm
+     *
+     * @param HashAlgorithm $hash
+     * @return void
+     */
+    public static function assertHash(HashAlgorithm $hash): void
+    {
+        switch ($hash) {
+            case HashAlgorithm::Unknown:
+            case HashAlgorithm::Md5:
+            case HashAlgorithm::Sha1:
+            case HashAlgorithm::Ripemd160:
+                throw new \RuntimeException(
+                    "Hash {$hash->name} is unsupported.",
+                );
+        }
+    }
+
+    /**
+     * Assert symmetric algorithm
+     *
+     * @param SymmetricAlgorithm $symmetric
+     * @return void
+     */
+    public static function assertSymmetric(SymmetricAlgorithm $symmetric): void
+    {
+        switch ($symmetric) {
+            case SymmetricAlgorithm::Plaintext:
+            case SymmetricAlgorithm::Idea:
+            case SymmetricAlgorithm::TripleDes:
+            case SymmetricAlgorithm::Cast5:
+                throw new \RuntimeException(
+                    "Symmetric {$symmetric->name} is unsupported.",
+                );
+        }
+    }
 }
diff --git a/src/Packet/AbstractPacket.php b/src/Packet/AbstractPacket.php
index cd4adef..772bda3 100644
--- a/src/Packet/AbstractPacket.php
+++ b/src/Packet/AbstractPacket.php
@@ -108,44 +108,6 @@ public function __toString(): string
      */
     abstract public function toBytes(): string;
 
-    /**
-     * Assert hash algorithm
-     *
-     * @param HashAlgorithm $hash
-     * @return void
-     */
-    protected static function assertHash(HashAlgorithm $hash): void
-    {
-        switch ($hash) {
-            case HashAlgorithm::Unknown:
-            case HashAlgorithm::Md5:
-            case HashAlgorithm::Sha1:
-            case HashAlgorithm::Ripemd160:
-                throw new \RuntimeException(
-                    "Hash {$hash->name} is unsupported.",
-                );
-        }
-    }
-
-    /**
-     * Assert symmetric algorithm
-     *
-     * @param SymmetricAlgorithm $symmetric
-     * @return void
-     */
-    protected static function assertSymmetric(SymmetricAlgorithm $symmetric): void
-    {
-        switch ($symmetric) {
-            case SymmetricAlgorithm::Plaintext:
-            case SymmetricAlgorithm::Idea:
-            case SymmetricAlgorithm::TripleDes:
-            case SymmetricAlgorithm::Cast5:
-                throw new \RuntimeException(
-                    "Symmetric {$symmetric->name} is unsupported.",
-                );
-        }
-    }
-
     /**
      * Encode package to the openpgp partial body specifier
      *
diff --git a/src/Packet/AeadEncryptedData.php b/src/Packet/AeadEncryptedData.php
index 6b1b8fe..7501e5f 100644
--- a/src/Packet/AeadEncryptedData.php
+++ b/src/Packet/AeadEncryptedData.php
@@ -8,7 +8,10 @@
 
 namespace OpenPGP\Packet;
 
-use OpenPGP\Common\Config;
+use OpenPGP\Common\{
+    Config,
+    Helper,
+};
 use OpenPGP\Enum\{
     AeadAlgorithm,
     PacketTag,
@@ -109,7 +112,7 @@ public static function encryptPackets(
         SymmetricAlgorithm $symmetric = SymmetricAlgorithm::Aes128,
     ): self
     {
-        self::assertSymmetric($symmetric);
+        Helper::assertSymmetric($symmetric);
 
         $aead = Config::getPreferredAead();
         $chunkSize = Config::getAeadChunkSize();
diff --git a/src/Packet/SecretKey.php b/src/Packet/SecretKey.php
index b450a35..a4961be 100644
--- a/src/Packet/SecretKey.php
+++ b/src/Packet/SecretKey.php
@@ -422,7 +422,7 @@ public function encrypt(
             $this->getLogger()->debug(
                 'Encrypt secret key material with passphrase.'
             );
-            self::assertSymmetric($symmetric);
+            Helper::assertSymmetric($symmetric);
 
             $aeadProtect = $aead instanceof AeadAlgorithm;
             if ($aeadProtect && $this->getVersion() !== PublicKey::VERSION_6) {
diff --git a/src/Packet/Signature.php b/src/Packet/Signature.php
index 93b2abb..ab48c6a 100644
--- a/src/Packet/Signature.php
+++ b/src/Packet/Signature.php
@@ -95,7 +95,7 @@ public function __construct(
             );
         }
         if ($version === self::VERSION_6) {
-            self::assertHash($hashAlgorithm);
+            Helper::assertHash($hashAlgorithm);
             if ($keyAlgorithm === KeyAlgorithm::Dsa) {
                 throw new \InvalidArgumentException(
                     "Public key {$keyAlgorithm->name} cannot be used with v{$version} signature packet.",
@@ -217,7 +217,7 @@ public static function createSignature(
         $version = $signKey->getVersion();
         $keyAlgorithm = $signKey->getKeyAlgorithm();
         $hashAlgorithm = $signKey->getPreferredHash($hashAlgorithm);
-        self::assertHash($hashAlgorithm);
+        Helper::assertHash($hashAlgorithm);
 
         $hashedSubpackets = [
             Signature\SignatureCreationTime::fromTime(
diff --git a/src/Packet/SymEncryptedData.php b/src/Packet/SymEncryptedData.php
index 11d4a43..5749b59 100644
--- a/src/Packet/SymEncryptedData.php
+++ b/src/Packet/SymEncryptedData.php
@@ -74,7 +74,7 @@ public static function encryptPackets(
         SymmetricAlgorithm $symmetric = SymmetricAlgorithm::Aes128,
     ): self
     {
-        self::assertSymmetric($symmetric);
+        Helper::assertSymmetric($symmetric);
         $cipher = $symmetric->cipherEngine(Config::CIPHER_MODE);
         $cipher->setKey($key);
         $cipher->setIV(str_repeat(self::ZERO_CHAR, $symmetric->blockSize()));
diff --git a/src/Packet/SymEncryptedIntegrityProtectedData.php b/src/Packet/SymEncryptedIntegrityProtectedData.php
index d9802b6..b1c3288 100644
--- a/src/Packet/SymEncryptedIntegrityProtectedData.php
+++ b/src/Packet/SymEncryptedIntegrityProtectedData.php
@@ -75,7 +75,7 @@ public function __construct(
         }
         $isV2 = $version === self::VERSION_2;
         if ($symmetric instanceof SymmetricAlgorithm && $isV2) {
-            self::assertSymmetric($symmetric);
+            Helper::assertSymmetric($symmetric);
         }
         if ($aead instanceof AeadAlgorithm && !$isV2) {
             throw new \InvalidArgumentException(
@@ -146,7 +146,7 @@ public static function encryptPackets(
     {
         $aeadProtect = $aead instanceof AeadAlgorithm;
         $version = $aeadProtect ? self::VERSION_2 : self::VERSION_1;
-        self::assertSymmetric($symmetric);
+        Helper::assertSymmetric($symmetric);
 
         $salt = '';
         $chunkSize = 0;
diff --git a/src/Packet/SymEncryptedSessionKey.php b/src/Packet/SymEncryptedSessionKey.php
index ee1d2a4..6e1797f 100644
--- a/src/Packet/SymEncryptedSessionKey.php
+++ b/src/Packet/SymEncryptedSessionKey.php
@@ -74,7 +74,7 @@ public function __construct(
             );
         }
         if ($version === self::VERSION_6) {
-            self::assertSymmetric($symmetric);
+            Helper::assertSymmetric($symmetric);
         }
         if ($aead instanceof AeadAlgorithm && $version < self::VERSION_5) {
             throw new \InvalidArgumentException(
@@ -154,7 +154,7 @@ public static function encryptSessionKey(
         $aeadProtect = $aead instanceof AeadAlgorithm;
         $version = $aeadProtect ? self::VERSION_6 : self::VERSION_4;
         $symmetric = $sessionKey?->getSymmetric() ?? $symmetric;
-        self::assertSymmetric($symmetric);
+        Helper::assertSymmetric($symmetric);
 
         $s2k = $aeadProtect && Argon2S2K::argon2Supported() ?
             Helper::stringToKey(S2kType::Argon2) :