diff --git a/IPython/parallel/apps/ipcontrollerapp.py b/IPython/parallel/apps/ipcontrollerapp.py
index 461988a..28f4eaf 100755
--- a/IPython/parallel/apps/ipcontrollerapp.py
+++ b/IPython/parallel/apps/ipcontrollerapp.py
@@ -367,7 +367,7 @@ class IPControllerApp(BaseParallelApplication):
         # IOPub relay (in a Process)
         q = mq(zmq.PUB, zmq.SUB, zmq.PUB, b'N/A',b'iopub')
         q.bind_in(f.client_url('iopub'))
-        q.setsockopt_in(zmq.IDENTITY, ident+"_iopub")
+        q.setsockopt_in(zmq.IDENTITY, ident + b"_iopub")
         q.bind_out(f.engine_url('iopub'))
         q.setsockopt_out(zmq.SUBSCRIBE, b'')
         q.connect_mon(monitor_url)
diff --git a/IPython/parallel/client/client.py b/IPython/parallel/client/client.py
index 0b06a36..a61036e 100644
--- a/IPython/parallel/client/client.py
+++ b/IPython/parallel/client/client.py
@@ -449,7 +449,7 @@ class Client(HasTraits):
         # configure and construct the session
         extra_args['packer'] = cfg['pack']
         extra_args['unpacker'] = cfg['unpack']
-        extra_args['key'] = cfg['exec_key']
+        extra_args['key'] = cast_bytes(cfg['exec_key'])
         
         self.session = Session(**extra_args)
 
diff --git a/IPython/parallel/controller/hub.py b/IPython/parallel/controller/hub.py
index 6f9dc89..49cdd67 100644
--- a/IPython/parallel/controller/hub.py
+++ b/IPython/parallel/controller/hub.py
@@ -896,7 +896,7 @@ class Hub(SessionFactory):
 
         content = dict(id=eid,status='ok')
         # check if requesting available IDs:
-        if uuid in self.by_ident:
+        if cast_bytes(uuid) in self.by_ident:
             try:
                 raise KeyError("uuid %r in use" % uuid)
             except:
@@ -1014,7 +1014,7 @@ class Hub(SessionFactory):
         self.ids.add(eid)
         self.keytable[eid] = ec.uuid
         self.engines[eid] = ec
-        self.by_ident[ec.uuid] = ec.id
+        self.by_ident[cast_bytes(ec.uuid)] = ec.id
         self.queues[eid] = list()
         self.tasks[eid] = list()
         self.completed[eid] = list()
diff --git a/IPython/parallel/controller/scheduler.py b/IPython/parallel/controller/scheduler.py
index a5a4ffe..39e2365 100644
--- a/IPython/parallel/controller/scheduler.py
+++ b/IPython/parallel/controller/scheduler.py
@@ -756,11 +756,11 @@ def launch_scheduler(in_addr, out_addr, mon_addr, not_addr, reg_addr, config=Non
         ctx = zmq.Context()
         loop = ioloop.IOLoop()
     ins = ZMQStream(ctx.socket(zmq.ROUTER),loop)
-    ins.setsockopt(zmq.IDENTITY, identity+'_in')
+    ins.setsockopt(zmq.IDENTITY, identity + b'_in')
     ins.bind(in_addr)
 
     outs = ZMQStream(ctx.socket(zmq.ROUTER),loop)
-    outs.setsockopt(zmq.IDENTITY, identity+'_out')
+    outs.setsockopt(zmq.IDENTITY, identity + b'_out')
     outs.bind(out_addr)
     mons = zmqstream.ZMQStream(ctx.socket(zmq.PUB),loop)
     mons.connect(mon_addr)