diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -1,3 +1,3 @@
-swh.core[db,http] >= 0.0.60
+swh.core[db,http] >= 0.0.70
 swh.model >= 0.0.40
 swh.storage >= 0.0.147
diff --git a/swh/journal/serializers.py b/swh/journal/serializers.py
--- a/swh/journal/serializers.py
+++ b/swh/journal/serializers.py
@@ -3,23 +3,13 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-import msgpack
-
+from swh.core.bencode import encode as bencode_encode
 from swh.core.api.serializers import msgpack_dumps, msgpack_loads
 
 
 def key_to_kafka(key):
     """Serialize a key, possibly a dict, in a predictable way"""
-    p = msgpack.Packer(use_bin_type=True)
-    if isinstance(key, dict):
-        return p.pack_map_pairs(sorted(key.items()))
-    else:
-        return p.pack(key)
-
-
-def kafka_to_key(kafka_key):
-    """Deserialize a key"""
-    return msgpack.loads(kafka_key)
+    return bencode_encode(key)
 
 
 def value_to_kafka(value):
diff --git a/swh/journal/tests/test_cli.py b/swh/journal/tests/test_cli.py
--- a/swh/journal/tests/test_cli.py
+++ b/swh/journal/tests/test_cli.py
@@ -140,7 +140,7 @@
         producer.produce(
             topic=kafka_prefix+'.content',
             key=key_to_kafka(sha1),
-            value=key_to_kafka({
+            value=value_to_kafka({
                 'sha1': sha1,
                 'status': 'visible',
             }),
diff --git a/swh/journal/tests/test_kafka_writer.py b/swh/journal/tests/test_kafka_writer.py
--- a/swh/journal/tests/test_kafka_writer.py
+++ b/swh/journal/tests/test_kafka_writer.py
@@ -13,9 +13,7 @@
 from swh.storage import get_storage
 
 from swh.journal.writer.kafka import KafkaJournalWriter
-from swh.journal.serializers import (
-    kafka_to_key, kafka_to_value
-)
+from swh.journal.serializers import kafka_to_value, key_to_kafka
 
 from .conftest import OBJECT_TYPE_KEYS
 
@@ -45,14 +43,15 @@
 
         fetched_messages += 1
         consumed_objects[msg.topic()].append(
-            (kafka_to_key(msg.key()), kafka_to_value(msg.value()))
+            (msg.key(), kafka_to_value(msg.value()))
         )
 
     for (object_type, (key_name, objects)) in OBJECT_TYPE_KEYS.items():
         topic = kafka_prefix + '.' + object_type
         (keys, values) = zip(*consumed_objects[topic])
         if key_name:
-            assert list(keys) == [object_[key_name] for object_ in objects]
+            assert list(keys) == [key_to_kafka(object_[key_name])
+                                  for object_ in objects]
         else:
             pass  # TODO
 
diff --git a/swh/journal/tests/test_replay.py b/swh/journal/tests/test_replay.py
--- a/swh/journal/tests/test_replay.py
+++ b/swh/journal/tests/test_replay.py
@@ -130,12 +130,12 @@
     # Note that flipping the order of these two insertions will crash
     # the test, because the legacy origin_format does not allow to create
     # the origin when needed (type is missing)
-    writer.send('origin', 'foo', {
+    writer.send('origin', b'foo', {
         'url': 'http://example.com/',
         'type': 'git',
     })
     for visit in visits:
-        writer.send('origin_visit', 'foo', visit)
+        writer.send('origin_visit', b'foo', visit)
 
     queue_size = len(queue)
 
diff --git a/swh/journal/tests/test_serializers.py b/swh/journal/tests/test_serializers.py
--- a/swh/journal/tests/test_serializers.py
+++ b/swh/journal/tests/test_serializers.py
@@ -3,7 +3,6 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-from collections import OrderedDict
 import itertools
 import unittest
 
@@ -14,15 +13,15 @@
     def test_key_to_kafka_repeatable(self):
         """Check the kafka key encoding is repeatable"""
         base_dict = {
-            'a': 'foo',
-            'b': 'bar',
-            'c': 'baz',
+            b'a': b'foo',
+            b'b': b'bar',
+            b'c': b'baz',
         }
 
         key = serializers.key_to_kafka(base_dict)
 
         for dict_keys in itertools.permutations(base_dict):
-            d = OrderedDict()
+            d = {}
             for k in dict_keys:
                 d[k] = base_dict[k]
 
diff --git a/swh/journal/writer/kafka.py b/swh/journal/writer/kafka.py
--- a/swh/journal/writer/kafka.py
+++ b/swh/journal/writer/kafka.py
@@ -63,15 +63,21 @@
             return object_['sha1']  # TODO: use a dict of hashes
         elif object_type == 'skipped_content':
             return {
-                hash: object_[hash]
+                hash.encode('ascii'): object_[hash]
                 for hash in DEFAULT_ALGORITHMS
             }
         elif object_type == 'origin':
-            return {'url': object_['url'], 'type': object_['type']}
+            return {
+                b'url': object_['url'].encode('ascii'),
+                b'type': object_['type'].encode('ascii')
+            }
         elif object_type == 'origin_visit':
             return {
-                'origin': object_['origin'],
-                'date': str(object_['date']),
+                b'origin': {
+                    b'url': object_['origin']['url'].encode('ascii'),
+                    b'type': object_['origin']['type'].encode('ascii'),
+                },
+                b'date': str(object_['date']).encode('ascii'),
             }
         else:
             raise ValueError('Unknown object type: %s.' % object_type)