diff --git a/ca_manager/gfk.py b/ca_manager/gfk.py
new file mode 100644
index 0000000..5f8d357
--- /dev/null
+++ b/ca_manager/gfk.py
@@ -0,0 +1,170 @@
+"""
+Provide a "Generic ForeignKey", similar to Django.  A "GFK" is composed of two
+columns: an object ID and an object type identifier.  The object types are
+collected in a global registry (all_models), so all you need to do is subclass
+``gfk.Model`` and your model will be added to the registry.
+
+Example:
+
+class Tag(Model):
+    tag = CharField()
+    object_type = CharField(null=True)
+    object_id = IntegerField(null=True)
+    object = GFKField('object_type', 'object_id')
+
+class Blog(Model):
+    tags = ReverseGFK(Tag, 'object_type', 'object_id')
+
+class Photo(Model):
+    tags = ReverseGFK(Tag, 'object_type', 'object_id')
+
+tag.object -> a blog or photo
+blog.tags -> select query of tags for ``blog`` instance
+Blog.tags -> select query of all tags for Blog instances
+"""
+
+from peewee import *
+from peewee import ModelBase as _BaseModel
+from peewee import Model as _Model
+from peewee import SelectQuery
+from peewee import Update as UpdateQuery
+from peewee import with_metaclass
+
+
+all_models = set()
+table_cache = {}
+
+
+class BaseModel(_BaseModel):
+    def __new__(cls, name, bases, attrs):
+        cls = super(BaseModel, cls).__new__(cls, name, bases, attrs)
+        if name not in ('_metaclass_helper_', 'Model'):
+            all_models.add(cls)
+        return cls
+
+class Model(with_metaclass(BaseModel, _Model)):
+    def __init__(self, *args, **kwargs):
+        self._obj_cache = {}
+        return super(Model, self).__init__(*args, **kwargs)
+
+
+def get_model(tbl_name):
+    if tbl_name not in table_cache:
+        for model in all_models:
+            if model._meta.table_name == tbl_name:
+                table_cache[tbl_name] = model
+                break
+    return table_cache.get(tbl_name)
+
+class BoundGFKField(object):
+    __slots__ = ('model', 'gfk_field')
+
+    def __init__(self, model, gfk_field):
+        self.model = model
+        self.gfk_field = gfk_field
+
+    @property
+    def unique(self):
+        indexes = self.model._meta.indexes
+        fields = set((self.gfk_field.model_type_field,
+                      self.gfk_field.model_id_field))
+        for (indexed_columns, is_unique) in indexes:
+            if not fields - set(indexed_columns):
+                return True
+        return False
+
+    @property
+    def primary_key(self):
+        pk = self.model._meta.primary_key
+        if isinstance(pk, CompositeKey):
+            fields = set((self.gfk_field.model_type_field,
+                          self.gfk_field.model_id_field))
+            if not fields - set(pk.field_names):
+                return True
+        return False
+
+    def __eq__(self, other):
+        meta = self.model._meta
+        type_field = meta.fields[self.gfk_field.model_type_field]
+        id_field = meta.fields[self.gfk_field.model_id_field]
+        return (
+            (type_field == other._meta.table_name) &
+            (id_field == other.get_id()))
+
+    def __ne__(self, other):
+        other_cls = type(other)
+        type_field = other._meta.fields[self.gfk_field.model_type_field]
+        id_field = other._meta.fields[self.gfk_field.model_id_field]
+        return (
+            (type_field == other._meta.table_name) &
+            (id_field != other.get_id()))
+
+
+class GFKField(object):
+    def __init__(self, model_type_field='object_type',
+                 model_id_field='object_id'):
+        self.model_type_field = model_type_field
+        self.model_id_field = model_id_field
+        self.att_name = '.'.join((self.model_type_field, self.model_id_field))
+
+    def get_obj(self, instance):
+        data = instance.__data__
+        if data.get(self.model_type_field) and data.get(self.model_id_field):
+            tbl_name = data[self.model_type_field]
+            model = get_model(tbl_name)
+            if not model:
+                raise AttributeError('Model for table "%s" not found in GFK '
+                                     'lookup.' % tbl_name)
+            query = model.select().where(
+                model._meta.primary_key == data[self.model_id_field])
+            return query.get()
+
+    def __get__(self, instance, instance_type=None):
+        if instance:
+            if self.att_name not in instance._obj_cache:
+                rel_obj = self.get_obj(instance)
+                if rel_obj:
+                    instance._obj_cache[self.att_name] = rel_obj
+            return instance._obj_cache.get(self.att_name)
+        return BoundGFKField(instance_type, self)
+
+    def __set__(self, instance, value):
+        instance._obj_cache[self.att_name] = value
+        instance.__data__[self.model_type_field] = value._meta.table_name
+        instance.__data__[self.model_id_field] = value.get_id()
+
+
+class ReverseGFK(object):
+    def __init__(self, model, model_type_field='object_type',
+                 model_id_field='object_id'):
+        self.model = model
+        self.model_type_field = model._meta.fields[model_type_field]
+        self.model_id_field = model._meta.fields[model_id_field]
+
+    def __get__(self, instance, instance_type=None):
+        if instance:
+            return self.model.select().where(
+                (self.model_type_field == instance._meta.table_name) &
+                (self.model_id_field == instance.get_id())
+            )
+        else:
+            return self.model.select().where(
+                self.model_type_field == instance_type._meta.table_name
+            )
+
+    def __set__(self, instance, value):
+        mtv = instance._meta.table_name
+        miv = instance.get_id()
+        if (isinstance(value, SelectQuery) and
+                value.model == self.model):
+            UpdateQuery(self.model, {
+                self.model_type_field: mtv,
+                self.model_id_field: miv,
+            }).where(value._where).execute()
+        elif all(map(lambda i: isinstance(i, self.model), value)):
+            for obj in value:
+                setattr(obj, self.model_type_field.name, mtv)
+                setattr(obj, self.model_id_field.name, miv)
+                obj.save()
+        else:
+            raise ValueError('ReverseGFK field unable to handle "%s"' % value)
diff --git a/ca_manager/manager.py b/ca_manager/manager.py
index aa843ac..56b1be0 100755
--- a/ca_manager/manager.py
+++ b/ca_manager/manager.py
@@ -6,8 +6,6 @@
 import shutil
 import subprocess
 
-from playhouse.gfk import *
-
 from .lookup import CALookup, RequestLookup, CertificateLookup
 
 from .models.ssh import SSHAuthority
diff --git a/ca_manager/models/authority.py b/ca_manager/models/authority.py
index d819bb9..8d8f2f6 100755
--- a/ca_manager/models/authority.py
+++ b/ca_manager/models/authority.py
@@ -1,8 +1,6 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-from playhouse.gfk import *
-
 from datetime import datetime
 
 import os
@@ -11,6 +9,7 @@
 from .customModel import CustomModel
 from .certificate import Certificate
 
+from ..gfk import *
 from ..paths import *
 
 __doc__ = """
@@ -49,8 +48,8 @@ class Authority(CustomModel):
             help_text='is root authority?',
             )
 
-    def __bool__(self):
-        return os.path.exists(self.path)
+#    def __bool__(self):
+#        return os.path.exists(self.path)
 
     @property
     def path(self):
@@ -86,5 +85,5 @@ def sign(self, request):
     def generate_certificate(self, request):
         raise NotImplementedError()
 
-    def __repr__(self):
+    def __str__(self):
         return ('%s %s (%s), created on %s' % (self.__class__.__name__, self.ca_id, self.name, self.creation_date))
diff --git a/ca_manager/models/certificate.py b/ca_manager/models/certificate.py
index 23cb29d..de7031e 100755
--- a/ca_manager/models/certificate.py
+++ b/ca_manager/models/certificate.py
@@ -1,13 +1,12 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-from playhouse.gfk import *
-
 import os
 import json
 
 from .customModel import CustomModel
 
+from ..gfk import *
 from ..paths import *
 
 
@@ -51,7 +50,7 @@ class Certificate(CustomModel):
                 help_text='certificate lifecycle state',
                 )
 
-    def __repr__(self):
+    def __str__(self):
         msg = """<%s:%s> for %s
                 signed %s by %s"""
         return (
diff --git a/ca_manager/models/customModel.py b/ca_manager/models/customModel.py
index c6c99b0..9d18e17 100644
--- a/ca_manager/models/customModel.py
+++ b/ca_manager/models/customModel.py
@@ -1,6 +1,6 @@
-from playhouse.gfk import *
 import os
 
+from ..gfk import *
 from ..paths import *
 
 custom_db = SqliteDatabase(os.path.join(MANAGER_PATH, 'ca_manager.db'))
diff --git a/ca_manager/models/ssh.py b/ca_manager/models/ssh.py
index 0e6b607..f2a119b 100644
--- a/ca_manager/models/ssh.py
+++ b/ca_manager/models/ssh.py
@@ -1,8 +1,6 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-from playhouse.gfk import *
-
 import os.path
 import subprocess
 
diff --git a/ca_manager/models/ssl.py b/ca_manager/models/ssl.py
index e4d93d8..9321112 100644
--- a/ca_manager/models/ssl.py
+++ b/ca_manager/models/ssl.py
@@ -1,8 +1,6 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-from playhouse.gfk import *
-
 import os
 from inspect import getsourcefile
 import subprocess
diff --git a/ca_manager/shell.py b/ca_manager/shell.py
index 1cb3931..4fc7f15 100755
--- a/ca_manager/shell.py
+++ b/ca_manager/shell.py
@@ -51,7 +51,7 @@ def do_describe_ca(self, l):
 
         ca = self.ca_manager.ca[argv[0]]
 
-        if ca:
+        if ca != None:
             ca_description = """
             Certification authority: %s
             --------------------------------------------------
diff --git a/requirements.txt b/requirements.txt
index e41b35e..27faf2d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1 @@
-appdirs==1.4.0
-packaging==16.8
-peewee==2.8.5
-six==1.10.0
+peewee==3.13.2
diff --git a/setup.py b/setup.py
index 9f4ac05..a5b1373 100644
--- a/setup.py
+++ b/setup.py
@@ -15,7 +15,7 @@
     ],
     install_requires=[
         'fqdn',
-        'peewee<3',
+        'peewee>=3',
     ],
     scripts=[
         'bin/ca-server',