diff --git a/django_etesync/migrations/0019_collectionmember.py b/django_etesync/migrations/0019_collectionmember.py
new file mode 100644
index 0000000..142e945
--- /dev/null
+++ b/django_etesync/migrations/0019_collectionmember.py
@@ -0,0 +1,29 @@
+# Generated by Django 3.0.3 on 2020-02-26 18:33
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('django_etesync', '0018_auto_20200226_1803'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='CollectionMember',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('encryptionKey', models.BinaryField(editable=True)),
+                ('accessLevel', models.CharField(choices=[('adm', 'Admin'), ('rw', 'Read Write'), ('ro', 'Read Only')], default='ro', max_length=3)),
+                ('collection', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='members', to='django_etesync.Collection')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'unique_together': {('user', 'collection')},
+            },
+        ),
+    ]
diff --git a/django_etesync/models.py b/django_etesync/models.py
index b11c36c..3be7b06 100644
--- a/django_etesync/models.py
+++ b/django_etesync/models.py
@@ -88,3 +88,25 @@ class CollectionItemRevision(models.Model):
 
     def __str__(self):
         return '{} {} current={}'.format(self.item.uid, self.id, self.current)
+
+
+class CollectionMember(models.Model):
+    class AccessLevels(models.TextChoices):
+        ADMIN = 'adm'
+        READ_WRITE = 'rw'
+        READ_ONLY = 'ro'
+
+    collection = models.ForeignKey(Collection, related_name='members', on_delete=models.CASCADE)
+    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
+    encryptionKey = models.BinaryField(editable=True, blank=False, null=False)
+    accessLevel = models.CharField(
+        max_length=3,
+        choices=AccessLevels.choices,
+        default=AccessLevels.READ_ONLY,
+    )
+
+    class Meta:
+        unique_together = ('user', 'collection')
+
+    def __str__(self):
+        return '{} {}'.format(self.collection.uid, self.user)
diff --git a/django_etesync/serializers.py b/django_etesync/serializers.py
index 8736a02..c194243 100644
--- a/django_etesync/serializers.py
+++ b/django_etesync/serializers.py
@@ -31,29 +31,25 @@ class BinaryBase64Field(serializers.Field):
 
 
 class CollectionSerializer(serializers.ModelSerializer):
-    owner = serializers.SlugRelatedField(
-        slug_field=User.USERNAME_FIELD,
-        read_only=True
-    )
     encryptionKey = serializers.SerializerMethodField('get_key_from_context')
-    permissions = serializers.SerializerMethodField('get_permission_from_context')
+    accessLevel = serializers.SerializerMethodField('get_access_level_from_context')
     ctag = serializers.SerializerMethodField('get_ctag')
 
     class Meta:
         model = models.Collection
-        fields = ('uid', 'version', 'owner', 'encryptionKey', 'permissions', 'ctag')
+        fields = ('uid', 'version', 'accessLevel', 'encryptionKey', 'ctag')
 
     def get_key_from_context(self, obj):
         request = self.context.get('request', None)
         if request is not None:
-            return 'FIXME'
+            return obj.members.get(user=request.user).encryptionKey
         return None
 
-    def get_permission_from_context(self, obj):
+    def get_access_level_from_context(self, obj):
         request = self.context.get('request', None)
         if request is not None:
-            return 'FIXME'
-        return 'readOnly'
+            return obj.members.get(user=request.user).accessLevel
+        return None
 
     def get_ctag(self, obj):
         return 'FIXME'