diff --git a/pisa/appointment.py b/common/appointment.py
similarity index 86%
rename from pisa/appointment.py
rename to common/appointment.py
index b4b9c0f..3b31365 100644
--- a/pisa/appointment.py
+++ b/common/appointment.py
@@ -1,4 +1,6 @@
 import json
+import struct
+from binascii import unhexlify
 
 from pisa.encrypted_blob import EncryptedBlob
 
@@ -101,3 +103,23 @@ class Appointment:
         appointment["triggered"] = triggered
 
         return json.dumps(appointment, sort_keys=True, separators=(",", ":"))
+
+    def serialize(self):
+        """
+        Serializes an appointment to be signed.
+
+        The serialization follows the same ordering as the fields in the appointment:
+            locator:start_time:end_time:to_self_delay:encrypted_blob
+
+        All values are big endian.
+
+        Returns:
+              :mod:`bytes`: The serialized data to be signed.
+        """
+        return (
+            unhexlify(self.locator)
+            + struct.pack(">I", self.start_time)
+            + struct.pack(">I", self.end_time)
+            + struct.pack(">I", self.to_self_delay)
+            + unhexlify(self.encrypted_blob.data)
+        )
diff --git a/common/cryptographer.py b/common/cryptographer.py
index 1cff63f..319d7f1 100644
--- a/common/cryptographer.py
+++ b/common/cryptographer.py
@@ -1,4 +1,3 @@
-import json
 from hashlib import sha256
 from binascii import unhexlify, hexlify
 
@@ -146,23 +145,6 @@ class Cryptographer:
 
         return blob
 
-    # NOTCOVERED
-    @staticmethod
-    def signature_format(data):
-        """
-        Serializes a given ``data`` in the right format to be signed.
-
-        Args:
-              data(:mod:`str`): the data to be formatted.
-
-        Returns:
-              :mod:`str`: The serialized data to be signed.
-        """
-
-        # FIXME: This is temporary serialization. A proper one is required. Data need to be unhexlified too (can't atm)
-        return json.dumps(data, sort_keys=True, separators=(",", ":")).encode("utf-8")
-
-    # Deserialize public key from der data.
     @staticmethod
     def load_public_key_der(pk_der):
         """
@@ -195,7 +177,6 @@ class Cryptographer:
 
         return None
 
-    # Deserialize private key from der data.
     @staticmethod
     def load_private_key_der(sk_der):
         """
@@ -231,7 +212,7 @@ class Cryptographer:
         Signs a given data using a given secret key using ECDSA.
 
         Args:
-            data(:mod:`str`): the data to be signed.
+            data(:mod:`bytes`): the data to be signed.
             sk(:mod:`EllipticCurvePrivateKey`): the ECDSA secret key used to signed the data.
             rtype: the return type for the encrypted value. Can be either ``'str'`` or ``'bytes'``.
 
@@ -263,7 +244,7 @@ class Cryptographer:
         Verifies if a signature is valid for a given public key and message.
 
         Args:
-            message(:mod:`str`): the message that is supposed have been signed.
+            message(:mod:`bytes`): the message that is supposed have been signed.
             signature(:mod:`str`): the potential signature of the message.
             pk(:mod:`EllipticCurvePublicKey`): the public key that is used to try to verify the signature.
 
diff --git a/test/pisa/unit/test_appointment.py b/test/common/unit/test_appointment.py
similarity index 98%
rename from test/pisa/unit/test_appointment.py
rename to test/common/unit/test_appointment.py
index 8af351e..d562667 100644
--- a/test/pisa/unit/test_appointment.py
+++ b/test/common/unit/test_appointment.py
@@ -2,7 +2,7 @@ import json
 from pytest import fixture
 
 from pisa import c_logger
-from pisa.appointment import Appointment
+from common.appointment import Appointment
 from pisa.encrypted_blob import EncryptedBlob
 
 from test.pisa.unit.conftest import get_random_value_hex