diff --git a/django_etebase/serializers.py b/django_etebase/serializers.py
index 2fe0a21..e7c0d50 100644
--- a/django_etebase/serializers.py
+++ b/django_etebase/serializers.py
@@ -64,6 +64,15 @@ class BinaryBase64Field(serializers.Field):
         return b64decode(data)
 
 
+# This field does nothing to the data. It's useful for raw binary data
+class RawField(serializers.Field):
+    def to_representation(self, value):
+        return value
+
+    def to_internal_value(self, data):
+        return data
+
+
 class CollectionEncryptionKeyField(BinaryBase64Field):
     def get_attribute(self, instance):
         request = self.context.get('request', None)
@@ -413,7 +422,7 @@ class AuthenticationLoginSerializer(serializers.Serializer):
 
 
 class AuthenticationLoginInnerSerializer(AuthenticationLoginChallengeSerializer):
-    challenge = BinaryBase64Field()
+    challenge = RawField()
     host = serializers.CharField()
     action = serializers.CharField()
 
diff --git a/django_etebase/views.py b/django_etebase/views.py
index 64acb18..c7fdab5 100644
--- a/django_etebase/views.py
+++ b/django_etebase/views.py
@@ -12,7 +12,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
-import json
+import msgpack
 from functools import reduce
 
 from django.conf import settings
@@ -72,6 +72,14 @@ from .serializers import (
 User = get_user_model()
 
 
+def msgpack_encode(content):
+    return msgpack.packb(content, use_bin_type=True)
+
+
+def msgpack_decode(content):
+    return msgpack.unpackb(content, raw=False)
+
+
 class BaseViewSet(viewsets.ModelViewSet):
     authentication_classes = tuple(app_settings.API_AUTHENTICATORS)
     permission_classes = tuple(app_settings.API_PERMISSIONS)
@@ -638,7 +646,7 @@ class AuthenticationViewSet(viewsets.ViewSet):
         enc_key = self.get_encryption_key(salt)
         box = nacl.secret.SecretBox(enc_key)
 
-        challenge_data = json.loads(box.decrypt(challenge).decode())
+        challenge_data = msgpack_decode(box.decrypt(challenge))
         now = int(datetime.now().timestamp())
         if action != expected_action:
             content = {'code': 'wrong_action', 'detail': 'Expected "{}" but got something else'.format(expected_action)}
@@ -680,8 +688,7 @@ class AuthenticationViewSet(viewsets.ViewSet):
                 "timestamp": int(datetime.now().timestamp()),
                 "userId": user.id,
             }
-            challenge = box.encrypt(json.dumps(
-                challenge_data, separators=(',', ':')).encode(), encoder=nacl.encoding.RawEncoder)
+            challenge = box.encrypt(msgpack_encode(challenge_data), encoder=nacl.encoding.RawEncoder)
 
             ret = {
                 "salt": b64encode(salt),
@@ -698,10 +705,11 @@ class AuthenticationViewSet(viewsets.ViewSet):
         outer_serializer.is_valid(raise_exception=True)
 
         response_raw = outer_serializer.validated_data['response']
-        response = json.loads(response_raw.decode())
+        response = msgpack_decode(response_raw)
         signature = outer_serializer.validated_data['signature']
 
-        serializer = AuthenticationLoginInnerSerializer(data=response, context={'host': request.get_host()})
+        context = {'host': request.get_host(), 'supports_binary': True}
+        serializer = AuthenticationLoginInnerSerializer(data=response, context=context)
         serializer.is_valid(raise_exception=True)
 
         bad_login_response = self.validate_login_request(
@@ -730,11 +738,11 @@ class AuthenticationViewSet(viewsets.ViewSet):
         outer_serializer.is_valid(raise_exception=True)
 
         response_raw = outer_serializer.validated_data['response']
-        response = json.loads(response_raw.decode())
+        response = msgpack_decode(response_raw)
         signature = outer_serializer.validated_data['signature']
 
-        serializer = AuthenticationChangePasswordInnerSerializer(
-            request.user.userinfo, data=response, context={'host': request.get_host()})
+        context = {'host': request.get_host(), 'supports_binary': True}
+        serializer = AuthenticationChangePasswordInnerSerializer(request.user.userinfo, data=response, context=context)
         serializer.is_valid(raise_exception=True)
 
         bad_login_response = self.validate_login_request(
diff --git a/requirements.in/base.txt b/requirements.in/base.txt
index 1ab0e9a..d27e110 100644
--- a/requirements.in/base.txt
+++ b/requirements.in/base.txt
@@ -4,5 +4,6 @@ django-cors-headers
 django-fullurl
 djangorestframework
 drf-nested-routers
+msgpack
 psycopg2-binary
 pynacl
diff --git a/requirements.txt b/requirements.txt
index 51b4d35..cd61ff1 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -15,6 +15,7 @@ django==3.0.3             # via -r requirements.in/base.txt, django-anymail, dja
 djangorestframework==3.11.0  # via -r requirements.in/base.txt, drf-nested-routers
 drf-nested-routers==0.91  # via -r requirements.in/base.txt
 idna==2.8                 # via requests
+msgpack==1.0.0            # via -r requirements.in/base.txt
 psycopg2-binary==2.8.4    # via -r requirements.in/base.txt
 pycparser==2.20           # via cffi
 pynacl==1.3.0             # via -r requirements.in/base.txt