diff --git a/helper/helper/base.py b/helper/helper/base.py
index 3429e142e..2739590bc 100644
--- a/helper/helper/base.py
+++ b/helper/helper/base.py
@@ -130,6 +130,13 @@ def __call__(self, action, target, params, event, signal, traversed=None):
             elif action in self.list_actions():
                 action_f = self.get_action(action)
                 args = inspect.signature(action_f).parameters
+                # Decode any serialized bytes parameters
+                for key, param in args.items():
+                    if param.annotation in (bytes, bytes | None):
+                        value = params.get(key, None)
+                        if value is not None:
+                            params[key] = decode_bytes(value)
+                # Add event and signal if requested
                 if "event" in args:
                     params["event"] = event
                 if "signal" in args:
diff --git a/helper/helper/management.py b/helper/helper/management.py
index cccfee3f2..003151e8f 100644
--- a/helper/helper/management.py
+++ b/helper/helper/management.py
@@ -90,15 +90,13 @@ def _await_reboot(self, serial, usb_enabled):
     def configure(
         self,
         reboot: bool = False,
-        cur_lock_code: str = "",
-        new_lock_code: str = "",
+        cur_lock_code: bytes | None = None,
+        new_lock_code: bytes | None = None,
         enabled_capabilities: dict = {},
         auto_eject_timeout: int | None = None,
         challenge_response_timeout: int | None = None,
         device_flags: int | None = None,
     ):
-        cur_code = bytes.fromhex(cur_lock_code) or None
-        new_code = bytes.fromhex(new_lock_code) or None
         config = DeviceConfig(
             enabled_capabilities,
             auto_eject_timeout,
@@ -106,7 +104,7 @@ def configure(
             DEVICE_FLAG(device_flags) if device_flags else None,
         )
         serial = self.session.read_device_info().serial
-        self.session.write_device_config(config, reboot, cur_code, new_code)
+        self.session.write_device_config(config, reboot, cur_lock_code, new_lock_code)
         flags = ["device_info"]
         if reboot:
             enabled = config.enabled_capabilities.get(TRANSPORT.USB)
diff --git a/helper/helper/oath.py b/helper/helper/oath.py
index c54016af2..383440445 100644
--- a/helper/helper/oath.py
+++ b/helper/helper/oath.py
@@ -142,13 +142,13 @@ def _remember_key(self, key):
         else:
             return False
 
-    def _get_key(self, key: str | None, password: str | None):
+    def _get_key(self, key: bytes | None, password: str | None):
         if key and password:
             raise ValueError("Only one of 'key' and 'password' can be provided.")
         if password:
             return self.session.derive_key(password)
         if key:
-            return decode_bytes(key)
+            return key
         raise ValueError("One of 'key' and 'password' must be provided.")
 
     def _set_key_verifier(self, key):
@@ -163,7 +163,7 @@ def _do_validate(self, key):
     @action
     def validate(
         self,
-        key: str | None = None,
+        key: bytes | None = None,
         password: str | None = None,
         remember: bool = False,
     ):
@@ -192,7 +192,7 @@ def validate(
     @action
     def set_key(
         self,
-        key: str | None = None,
+        key: bytes | None = None,
         password: str | None = None,
         remember: bool = False,
     ):
diff --git a/helper/helper/piv.py b/helper/helper/piv.py
index 0ad166fcd..a86c933ae 100644
--- a/helper/helper/piv.py
+++ b/helper/helper/piv.py
@@ -201,9 +201,9 @@ def verify_pin(self, signal, pin: str):
         return dict(status=True, authenticated=self._authenticated)
 
     @action
-    def authenticate(self, signal, key: str):
+    def authenticate(self, signal, key: bytes):
         try:
-            self._authenticate(bytes.fromhex(key), signal)
+            self._authenticate(key, signal)
             return dict(status=True)
         except ApduError as e:
             if e.sw == SW.SECURITY_CONDITION_NOT_SATISFIED:
@@ -213,14 +213,13 @@ def authenticate(self, signal, key: str):
     @action(condition=lambda self: self._authenticated)
     def set_key(
         self,
-        params,
-        key: str,
+        key: bytes,
         key_type: int = MANAGEMENT_KEY_TYPE.TDES,
         store_key: bool = False,
     ):
         pivman_set_mgm_key(
             self.session,
-            bytes.fromhex(key),
+            key,
             MANAGEMENT_KEY_TYPE(key_type),
             False,
             store_key,
@@ -264,9 +263,9 @@ def slots(self):
         return SlotsNode(self.session)
 
     @action(closes_child=False)
-    def examine_file(self, data: str, password: str | None = None):
+    def examine_file(self, data: bytes, password: str | None = None):
         try:
-            private_key, certs = _parse_file(bytes.fromhex(data), password)
+            private_key, certs = _parse_file(data, password)
             certificate = _choose_cert(certs)
 
             return dict(
@@ -461,9 +460,9 @@ def move_key(
         return dict()
 
     @action
-    def import_file(self, data: str, password: str | None = None, **kwargs):
+    def import_file(self, data: bytes, password: str | None = None, **kwargs):
         try:
-            private_key, certs = _parse_file(bytes.fromhex(data), password)
+            private_key, certs = _parse_file(data, password)
         except InvalidPasswordError:
             logger.debug("Invalid or missing password", exc_info=True)
             raise ValueError("Wrong/Missing password")
diff --git a/helper/helper/yubiotp.py b/helper/helper/yubiotp.py
index feb37bf33..098400e50 100644
--- a/helper/helper/yubiotp.py
+++ b/helper/helper/yubiotp.py
@@ -12,7 +12,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-from .base import RpcNode, action, child
+from .base import RpcNode, action, child, decode_bytes
 
 from yubikit.core import NotSupportedError, CommandError
 from yubikit.core.otp import modhex_encode, modhex_decode
@@ -95,15 +95,15 @@ def format_yubiotp_csv(
         self,
         serial: int,
         public_id: str,
-        private_id: str,
-        key: str,
+        private_id: bytes,
+        key: bytes,
     ):
         return dict(
             csv=format_csv(
                 serial,
                 modhex_decode(public_id),
-                bytes.fromhex(private_id),
-                bytes.fromhex(key),
+                private_id,
+                key,
             )
         )
 
@@ -145,19 +145,16 @@ def _can_calculate(self, slot):
             return False
 
     @action(condition=lambda self: self._maybe_configured(self.slot))
-    def delete(self, curr_acc_code: str | None = None):
+    def delete(self, curr_acc_code: bytes | None = None):
         try:
-            access_code = bytes.fromhex(curr_acc_code) if curr_acc_code else None
-            self.session.delete_slot(self.slot, access_code)
+            self.session.delete_slot(self.slot, curr_acc_code)
             return dict()
         except CommandError:
             raise ValueError(_FAIL_MSG)
 
     @action(condition=lambda self: self._can_calculate(self.slot))
-    def calculate(self, event, challenge: str):
-        response = self.session.calculate_hmac_sha1(
-            self.slot, bytes.fromhex(challenge), event
-        )
+    def calculate(self, event, challenge: bytes):
+        response = self.session.calculate_hmac_sha1(self.slot, challenge, event)
         return dict(response=response)
 
     @staticmethod
@@ -189,13 +186,13 @@ def _apply_options(config, options) -> None:
 
         if "token_id" in options:
             token_id, *args = options.pop("token_id")
-            config.token_id(bytes.fromhex(token_id), *args)
+            config.token_id(decode_bytes(token_id), *args)
 
     @staticmethod
     def _get_config(cfg_type: str, **kwargs) -> SlotConfiguration:
         match cfg_type:
             case "hmac_sha1":
-                return HmacSha1SlotConfiguration(bytes.fromhex(kwargs["key"]))
+                return HmacSha1SlotConfiguration(decode_bytes(kwargs["key"]))
             case "hotp":
                 return HotpSlotConfiguration(parse_b32_key(kwargs["key"]))
             case "static_password":
@@ -207,8 +204,8 @@ def _get_config(cfg_type: str, **kwargs) -> SlotConfiguration:
             case "yubiotp":
                 return YubiOtpSlotConfiguration(
                     fixed=modhex_decode(kwargs["public_id"]),
-                    uid=bytes.fromhex(kwargs["private_id"]),
-                    key=bytes.fromhex(kwargs["key"]),
+                    uid=decode_bytes(kwargs["private_id"]),
+                    key=decode_bytes(kwargs["key"]),
                 )
             case unsupported:
                 raise ValueError(
@@ -217,17 +214,20 @@ def _get_config(cfg_type: str, **kwargs) -> SlotConfiguration:
 
     @action
     def put(
-        self, type: str, options: dict = {}, curr_acc_code: str | None = None, **kwargs
+        self,
+        type: str,
+        options: dict = {},
+        curr_acc_code: bytes | None = None,
+        **kwargs,
     ):
-        access_code = bytes.fromhex(curr_acc_code) if curr_acc_code else None
         config = self._get_config(type, **kwargs)
         self._apply_options(config, options)
         try:
             self.session.put_configuration(
                 self.slot,
                 config,
-                access_code,
-                access_code,
+                curr_acc_code,
+                curr_acc_code,
             )
             return dict()
         except CommandError:
@@ -240,8 +240,8 @@ def put(
     def update(
         self,
         params,
-        acc_code: str | None = None,
-        curr_acc_code: str | None = None,
+        acc_code: bytes | None = None,
+        curr_acc_code: bytes | None = None,
         **kwargs,
     ):
         config = UpdateConfiguration()
@@ -249,7 +249,7 @@ def update(
         self.session.update_configuration(
             self.slot,
             config,
-            bytes.fromhex(acc_code) if acc_code else None,
-            bytes.fromhex(curr_acc_code) if curr_acc_code else None,
+            acc_code,
+            curr_acc_code,
         )
         return dict()