diff --git a/src/Makefile.am b/src/Makefile.am
index 32f088e9..f19c0f65 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -57,6 +57,7 @@ libzmq_la_SOURCES = app_thread.hpp \
     atomic_bitmap.hpp \
     atomic_counter.hpp \
     atomic_ptr.hpp \
+    blob.hpp \
     command.hpp \
     config.hpp \
     decoder.hpp \
diff --git a/src/blob.hpp b/src/blob.hpp
new file mode 100644
index 00000000..a4fa8cd9
--- /dev/null
+++ b/src/blob.hpp
@@ -0,0 +1,33 @@
+/*
+    Copyright (c) 2007-2010 iMatix Corporation
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the Lesser GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    Lesser GNU General Public License for more details.
+
+    You should have received a copy of the Lesser GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZMQ_BLOB_HPP_INCLUDED__
+#define __ZMQ_BLOB_HPP_INCLUDED__
+
+#include <string>
+
+namespace zmq
+{
+
+    //  Object to hold dynamically allocated opaque binary data.
+    typedef std::basic_string <unsigned char> blob_t;
+
+}
+
+#endif
diff --git a/src/i_engine.hpp b/src/i_engine.hpp
index bcb42976..d64027dd 100644
--- a/src/i_engine.hpp
+++ b/src/i_engine.hpp
@@ -22,6 +22,8 @@
 
 #include <stddef.h>
 
+#include "blob.hpp"
+
 namespace zmq
 {
 
@@ -42,8 +44,7 @@ namespace zmq
         //  Start tracing the message route. Engine should add the identity
         //  supplied to all inbound messages and trim identity from all the
         //  outbound messages.
-        virtual void traceroute (unsigned char *identity_,
-            size_t identity_size_) = 0;
+        virtual void traceroute (const blob_t &identity_) = 0;
     };
 
 }
diff --git a/src/object.cpp b/src/object.cpp
index 73a17a37..eaa67c9a 100644
--- a/src/object.cpp
+++ b/src/object.cpp
@@ -83,8 +83,8 @@ void zmq::object_t::process_command (command_t &cmd_)
 
     case command_t::attach:
         process_attach (cmd_.args.attach.engine,
-            cmd_.args.attach.peer_identity_size,
-            cmd_.args.attach.peer_identity);
+            blob_t (cmd_.args.attach.peer_identity,
+            cmd_.args.attach.peer_identity_size));
         process_seqnum ();
         break;
 
@@ -184,8 +184,7 @@ void zmq::object_t::send_own (socket_base_t *destination_, owned_t *object_)
 }
 
 void zmq::object_t::send_attach (session_t *destination_, i_engine *engine_,
-    unsigned char peer_identity_size_, unsigned char *peer_identity_,
-    bool inc_seqnum_)
+    const blob_t &peer_identity_, bool inc_seqnum_)
 {
     if (inc_seqnum_)
         destination_->inc_seqnum ();
@@ -194,17 +193,17 @@ void zmq::object_t::send_attach (session_t *destination_, i_engine *engine_,
     cmd.destination = destination_;
     cmd.type = command_t::attach;
     cmd.args.attach.engine = engine_;
-    if (!peer_identity_size_) {
+    if (peer_identity_.empty ()) {
         cmd.args.attach.peer_identity_size = 0;
         cmd.args.attach.peer_identity = NULL;
     }
     else {
-        cmd.args.attach.peer_identity_size = peer_identity_size_;
+        cmd.args.attach.peer_identity_size = peer_identity_.size ();
         cmd.args.attach.peer_identity =
-            (unsigned char*) malloc (peer_identity_size_);
+            (unsigned char*) malloc (peer_identity_.size ());
         zmq_assert (cmd.args.attach.peer_identity_size);
-        memcpy (cmd.args.attach.peer_identity, peer_identity_,
-            peer_identity_size_);
+        memcpy (cmd.args.attach.peer_identity, peer_identity_.data (),
+            peer_identity_.size ());
     }
     send_command (cmd);
 }
@@ -289,7 +288,7 @@ void zmq::object_t::process_own (owned_t *object_)
 }
 
 void zmq::object_t::process_attach (i_engine *engine_,
-    unsigned char peer_identity_size_, unsigned char *peer_identity_)
+    const blob_t &peer_identity_)
 {
     zmq_assert (false);
 }
diff --git a/src/object.hpp b/src/object.hpp
index 4c82a0d8..d4926952 100644
--- a/src/object.hpp
+++ b/src/object.hpp
@@ -21,6 +21,7 @@
 #define __ZMQ_OBJECT_HPP_INCLUDED__
 
 #include "stdint.hpp"
+#include "blob.hpp"
 
 namespace zmq
 {
@@ -64,8 +65,8 @@ namespace zmq
         void send_own (class socket_base_t *destination_,
             class owned_t *object_);
         void send_attach (class session_t *destination_,
-            struct i_engine *engine_, unsigned char peer_identity_size_,
-            unsigned char *peer_identity_, bool inc_seqnum_ = true);
+             struct i_engine *engine_, const blob_t &peer_identity_,
+             bool inc_seqnum_ = true);
         void send_bind (class socket_base_t *destination_,
              class reader_t *in_pipe_, class writer_t *out_pipe_,
              bool inc_seqnum_ = true);
@@ -83,7 +84,7 @@ namespace zmq
         virtual void process_plug ();
         virtual void process_own (class owned_t *object_);
         virtual void process_attach (struct i_engine *engine_,
-             unsigned char peer_identity_size_, unsigned char *peer_identity_);
+            const blob_t &peer_identity_);
         virtual void process_bind (class reader_t *in_pipe_,
             class writer_t *out_pipe_);
         virtual void process_revive ();
diff --git a/src/pgm_receiver.cpp b/src/pgm_receiver.cpp
index a2ba9c65..b7ca3278 100644
--- a/src/pgm_receiver.cpp
+++ b/src/pgm_receiver.cpp
@@ -88,8 +88,7 @@ void zmq::pgm_receiver_t::revive ()
     zmq_assert (false);
 }
 
-void zmq::pgm_receiver_t::traceroute (unsigned char *identity_,
-    size_t identity_size_)
+void zmq::pgm_receiver_t::traceroute (const blob_t &identity_)
 {
     //  No need for tracerouting functionality in PGM socket at the moment.
     zmq_assert (false);
diff --git a/src/pgm_receiver.hpp b/src/pgm_receiver.hpp
index f03551fa..b01e5b0f 100644
--- a/src/pgm_receiver.hpp
+++ b/src/pgm_receiver.hpp
@@ -54,7 +54,7 @@ namespace zmq
         void plug (struct i_inout *inout_);
         void unplug ();
         void revive ();
-        void traceroute (unsigned char *identity_, size_t identity_size_);
+        void traceroute (const blob_t &identity_);
 
         //  i_poll_events interface implementation.
         void in_event ();
diff --git a/src/pgm_sender.cpp b/src/pgm_sender.cpp
index fa7d7e0c..acbc3fb4 100644
--- a/src/pgm_sender.cpp
+++ b/src/pgm_sender.cpp
@@ -102,8 +102,7 @@ void zmq::pgm_sender_t::revive ()
     out_event ();
 }
 
-void zmq::pgm_sender_t::traceroute (unsigned char *identity_,
-    size_t identity_size_)
+void zmq::pgm_sender_t::traceroute (const blob_t &identity_)
 {
     //  No need for tracerouting functionality in PGM socket at the moment.
     zmq_assert (false);
diff --git a/src/pgm_sender.hpp b/src/pgm_sender.hpp
index 89357f5c..70416101 100644
--- a/src/pgm_sender.hpp
+++ b/src/pgm_sender.hpp
@@ -52,7 +52,7 @@ namespace zmq
         void plug (struct i_inout *inout_);
         void unplug ();
         void revive ();
-        void traceroute (unsigned char *identity_, size_t identity_size_);
+        void traceroute (const blob_t &identity_);
 
         //  i_poll_events interface implementation.
         void in_event ();
diff --git a/src/session.cpp b/src/session.cpp
index 1fab3c28..b2393d85 100644
--- a/src/session.cpp
+++ b/src/session.cpp
@@ -40,24 +40,18 @@ zmq::session_t::session_t (object_t *parent_, socket_base_t *owner_,
 }
 
 zmq::session_t::session_t (object_t *parent_, socket_base_t *owner_,
-      const options_t &options_, unsigned char peer_identity_size_,
-      unsigned char *peer_identity_) :
+      const options_t &options_, const blob_t &peer_identity_) :
     owned_t (parent_, owner_),
     in_pipe (NULL),
     active (true),
     out_pipe (NULL),
     engine (NULL),
     ordinal (0),
+    peer_identity (peer_identity_),
     options (options_)
 {
-
-if (!peer_identity_size_)
-
-    //  If peer identity is not supplied, leave it empty.
-    if (peer_identity_size_) {
-        peer_identity.assign ((char*) peer_identity_, peer_identity_size_);
-        if (!owner->register_session (peer_identity_size_, peer_identity_,
-              this)) {
+    if (!peer_identity.empty ()) {
+        if (!owner->register_session (peer_identity, this)) {
 
             //  TODO: There's already a session with the specified
             //  identity. We should presumably syslog it and drop the
@@ -180,8 +174,7 @@ void zmq::session_t::process_unplug ()
     if (ordinal)
         owner->unregister_session (ordinal);
     else if (!peer_identity.empty ())
-        owner->unregister_session ((unsigned char) peer_identity.size (),
-            (unsigned char*) peer_identity.data ());
+        owner->unregister_session (peer_identity);
 
     //  Ask associated pipes to terminate.
     if (in_pipe) {
@@ -201,26 +194,23 @@ void zmq::session_t::process_unplug ()
 }
 
 void zmq::session_t::process_attach (i_engine *engine_,
-    unsigned char peer_identity_size_, unsigned char *peer_identity_)
+    const blob_t &peer_identity_)
 {
     if (!peer_identity.empty ()) {
 
         //  If we already know the peer name do nothing, just check whether
         //  it haven't changed.
-        zmq_assert (peer_identity.size () == peer_identity_size_);
-        zmq_assert (memcmp (peer_identity.data (), peer_identity_,
-            peer_identity_size_) == 0);
+        zmq_assert (peer_identity == peer_identity_);
     }
-    else if (peer_identity_size_) {
+    else if (!peer_identity_.empty ()) {
 
-        //  Remember the peer identity.
-        peer_identity.assign ((char*) peer_identity_, peer_identity_size_);
+        //  Store the peer identity.
+        peer_identity = peer_identity_;
 
         //  If the session is not registered with the ordinal, let's register
         //  it using the peer name.
         if (!ordinal) {
-            if (!owner->register_session (peer_identity_size_, peer_identity_,
-                  this)) {
+            if (!owner->register_session (peer_identity, this)) {
 
                 //  TODO: There's already a session with the specified
                 //  identity. We should presumably syslog it and drop the
diff --git a/src/session.hpp b/src/session.hpp
index 7607cfbd..d4127285 100644
--- a/src/session.hpp
+++ b/src/session.hpp
@@ -20,12 +20,11 @@
 #ifndef __ZMQ_SESSION_HPP_INCLUDED__
 #define __ZMQ_SESSION_HPP_INCLUDED__
 
-#include <string>
-
 #include "i_inout.hpp"
 #include "i_endpoint.hpp"
 #include "owned.hpp"
 #include "options.hpp"
+#include "blob.hpp"
 
 namespace zmq
 {
@@ -38,11 +37,9 @@ namespace zmq
         session_t (object_t *parent_, socket_base_t *owner_,
             const options_t &options_);
 
-        //  Creates named session. If name is NULL, transient session with
-        //  auto-generated name is created.
+        //  Creates named session.
         session_t (object_t *parent_, socket_base_t *owner_,
-            const options_t &options_, unsigned char peer_identity_size_,
-            unsigned char *peer_identity_);
+            const options_t &options_, const blob_t &peer_identity_);
 
         //  i_inout interface implementation.
         bool read (::zmq_msg_t *msg_);
@@ -68,7 +65,7 @@ namespace zmq
         void process_plug ();
         void process_unplug ();
         void process_attach (struct i_engine *engine_,
-            unsigned char peer_identity_size_, unsigned char *peer_identity_);
+            const blob_t &peer_identity_);
 
         //  Inbound pipe, i.e. one the session is getting messages from.
         class reader_t *in_pipe;
@@ -87,7 +84,7 @@ namespace zmq
         uint64_t ordinal;
 
         //  Identity of the peer.
-        std::string peer_identity;
+        blob_t peer_identity;
 
         //  Inherited socket options.
         options_t options;
diff --git a/src/socket_base.cpp b/src/socket_base.cpp
index 4af69a01..7d90236c 100644
--- a/src/socket_base.cpp
+++ b/src/socket_base.cpp
@@ -267,7 +267,7 @@ int zmq::socket_base_t::connect (const char *addr_)
                 return -1;
             }
 
-            send_attach (session, pgm_sender, 0, NULL);
+            send_attach (session, pgm_sender, blob_t ());
         }
         else if (options.requires_in) {
 
@@ -282,7 +282,7 @@ int zmq::socket_base_t::connect (const char *addr_)
                 return -1;
             }
 
-            send_attach (session, pgm_receiver, 0, NULL);
+            send_attach (session, pgm_receiver, blob_t ());
         }
         else
             zmq_assert (false);
@@ -454,33 +454,29 @@ bool zmq::socket_base_t::has_out ()
     return xhas_out ();
 }
 
-bool zmq::socket_base_t::register_session (unsigned char peer_identity_size_,
-    unsigned char *peer_identity_, session_t *session_)
+bool zmq::socket_base_t::register_session (const blob_t &peer_identity_,
+    session_t *session_)
 {
     sessions_sync.lock ();
-    bool registered = named_sessions.insert (std::make_pair (std::string (
-            (char*) peer_identity_, peer_identity_size_), session_)).second;
+    bool registered = named_sessions.insert (
+        std::make_pair (peer_identity_, session_)).second;
     sessions_sync.unlock ();
     return registered;
 }
 
-void zmq::socket_base_t::unregister_session (unsigned char peer_identity_size_,
-    unsigned char *peer_identity_)
+void zmq::socket_base_t::unregister_session (const blob_t &peer_identity_)
 {
     sessions_sync.lock ();
-    named_sessions_t::iterator it = named_sessions.find (std::string (
-        (char*) peer_identity_, peer_identity_size_));
+    named_sessions_t::iterator it = named_sessions.find (peer_identity_);
     zmq_assert (it != named_sessions.end ());
     named_sessions.erase (it);
     sessions_sync.unlock ();
 }
 
-zmq::session_t *zmq::socket_base_t::find_session (
-    unsigned char peer_identity_size_, unsigned char *peer_identity_)
+zmq::session_t *zmq::socket_base_t::find_session (const blob_t &peer_identity_)
 {
     sessions_sync.lock ();
-    named_sessions_t::iterator it = named_sessions.find (std::string (
-        (char*) peer_identity_, peer_identity_size_));
+    named_sessions_t::iterator it = named_sessions.find (peer_identity_);
     if (it == named_sessions.end ()) {
         sessions_sync.unlock ();
         return NULL;
diff --git a/src/socket_base.hpp b/src/socket_base.hpp
index a2878ea4..39f09de0 100644
--- a/src/socket_base.hpp
+++ b/src/socket_base.hpp
@@ -23,7 +23,6 @@
 #include <set>
 #include <map>
 #include <vector>
-#include <string>
 
 #include "../bindings/c/zmq.h"
 
@@ -35,6 +34,7 @@
 #include "stdint.hpp"
 #include "atomic_counter.hpp"
 #include "stdint.hpp"
+#include "blob.hpp"
 
 namespace zmq
 {
@@ -78,12 +78,10 @@ namespace zmq
         //  There are two distinct types of sessions: those identified by name
         //  and those identified by ordinal number. Thus two sets of session
         //  management functions.
-        bool register_session (unsigned char peer_identity_size_,
-            unsigned char *peer_identity_, class session_t *session_);
-        void unregister_session (unsigned char peer_identity_size_,
-            unsigned char *peer_identity_);
-        class session_t *find_session (unsigned char peer_identity_size_,
-            unsigned char *peer_identity_);
+        bool register_session (const blob_t &peer_identity_,
+            class session_t *session_);
+        void unregister_session (const blob_t &peer_identity_);
+        class session_t *find_session (const blob_t &peer_identity_);
         uint64_t register_session (class session_t *session_);
         void unregister_session (uint64_t ordinal_);
         class session_t *find_session (uint64_t ordinal_);
@@ -158,7 +156,7 @@ namespace zmq
         //  within the socket, instead they are used by I/O objects owned by
         //  the socket. As those objects can live in different threads,
         //  the access is synchronised by mutex.
-        typedef std::map <std::string, session_t*> named_sessions_t;
+        typedef std::map <blob_t, session_t*> named_sessions_t;
         named_sessions_t named_sessions;
         typedef std::map <uint64_t, session_t*> unnamed_sessions_t;
         unnamed_sessions_t unnamed_sessions;
diff --git a/src/zmq_decoder.cpp b/src/zmq_decoder.cpp
index f502ffdb..20e07bc3 100644
--- a/src/zmq_decoder.cpp
+++ b/src/zmq_decoder.cpp
@@ -27,9 +27,7 @@
 
 zmq::zmq_decoder_t::zmq_decoder_t (size_t bufsize_) :
     decoder_t <zmq_decoder_t> (bufsize_),
-    destination (NULL),
-    prefix (NULL),
-    prefix_size (0)
+    destination (NULL)
 {
     zmq_msg_init (&in_progress);
 
@@ -39,9 +37,6 @@ zmq::zmq_decoder_t::zmq_decoder_t (size_t bufsize_) :
 
 zmq::zmq_decoder_t::~zmq_decoder_t ()
 {
-    if (prefix)
-        free (prefix);
-
     zmq_msg_close (&in_progress);
 }
 
@@ -50,13 +45,9 @@ void zmq::zmq_decoder_t::set_inout (i_inout *destination_)
     destination = destination_;
 }
 
-void zmq::zmq_decoder_t::add_prefix (unsigned char *prefix_,
-    size_t prefix_size_)
+void zmq::zmq_decoder_t::add_prefix (const blob_t &prefix_)
 {
-    prefix = malloc (prefix_size_);
-    zmq_assert (prefix);
-    memcpy (prefix, prefix_, prefix_size_);
-    prefix_size = prefix_size_;
+    prefix = prefix_;
 }
 
 bool zmq::zmq_decoder_t::one_byte_size_ready ()
@@ -72,15 +63,16 @@ bool zmq::zmq_decoder_t::one_byte_size_ready ()
         //  in_progress is initialised at this point so in theory we should
         //  close it before calling zmq_msg_init_size, however, it's a 0-byte
         //  message and thus we can treat it as uninitialised...
-        int rc = zmq_msg_init_size (&in_progress, prefix_size + *tmpbuf);
+        int rc = zmq_msg_init_size (&in_progress, prefix.size () + *tmpbuf);
         errno_assert (rc == 0);
 
         //  Fill in the message prefix if any.
-        if (prefix)
-            memcpy (zmq_msg_data (&in_progress), prefix, prefix_size);
+        if (!prefix.empty ())
+            memcpy (zmq_msg_data (&in_progress), prefix.data (),
+                prefix.size ());
 
-        next_step ((unsigned char*) zmq_msg_data (&in_progress) + prefix_size,
-            *tmpbuf, &zmq_decoder_t::message_ready);
+        next_step ((unsigned char*) zmq_msg_data (&in_progress) +
+            prefix.size (), *tmpbuf, &zmq_decoder_t::message_ready);
     }
     return true;
 }
@@ -95,14 +87,14 @@ bool zmq::zmq_decoder_t::eight_byte_size_ready ()
     //  in_progress is initialised at this point so in theory we should
     //  close it before calling zmq_msg_init_size, however, it's a 0-byte
     //  message and thus we can treat it as uninitialised...
-    int rc = zmq_msg_init_size (&in_progress, prefix_size + size);
+    int rc = zmq_msg_init_size (&in_progress, prefix.size () + size);
     errno_assert (rc == 0);
 
     //  Fill in the message prefix if any.
-    if (prefix)
-        memcpy (zmq_msg_data (&in_progress), prefix, prefix_size);
+    if (!prefix.empty ())
+        memcpy (zmq_msg_data (&in_progress), prefix.data (), prefix.size ());
 
-    next_step ((unsigned char*) zmq_msg_data (&in_progress) + prefix_size ,
+    next_step ((unsigned char*) zmq_msg_data (&in_progress) + prefix.size (),
         size, &zmq_decoder_t::message_ready);
     return true;
 }
diff --git a/src/zmq_decoder.hpp b/src/zmq_decoder.hpp
index dfabecee..11ee6c2f 100644
--- a/src/zmq_decoder.hpp
+++ b/src/zmq_decoder.hpp
@@ -23,6 +23,7 @@
 #include "../bindings/c/zmq.h"
 
 #include "decoder.hpp"
+#include "blob.hpp"
 
 namespace zmq
 {
@@ -41,7 +42,7 @@ namespace zmq
 
         //  Once called, all decoded messages will be prefixed by the specified
         //  prefix.
-        void add_prefix (unsigned char *prefix_, size_t prefix_size_);
+        void add_prefix (const blob_t &prefix_);
 
     private:
 
@@ -53,8 +54,7 @@ namespace zmq
         unsigned char tmpbuf [8];
         ::zmq_msg_t in_progress;
 
-        void *prefix;
-        size_t prefix_size;
+        blob_t prefix;
 
         zmq_decoder_t (const zmq_decoder_t&);
         void operator = (const zmq_decoder_t&);
diff --git a/src/zmq_engine.cpp b/src/zmq_engine.cpp
index bda098c5..75f34416 100644
--- a/src/zmq_engine.cpp
+++ b/src/zmq_engine.cpp
@@ -160,11 +160,10 @@ void zmq::zmq_engine_t::revive ()
     out_event ();
 }
 
-void zmq::zmq_engine_t::traceroute (unsigned char *identity_,
-    size_t identity_size_)
+void zmq::zmq_engine_t::traceroute (const blob_t &identity_)
 {
     encoder.trim_prefix ();
-    decoder.add_prefix (identity_, identity_size_);
+    decoder.add_prefix (identity_);
 }
 
 void zmq::zmq_engine_t::error ()
diff --git a/src/zmq_engine.hpp b/src/zmq_engine.hpp
index 174dd1a2..8657e8e1 100644
--- a/src/zmq_engine.hpp
+++ b/src/zmq_engine.hpp
@@ -47,7 +47,7 @@ namespace zmq
         void plug (struct i_inout *inout_);
         void unplug ();
         void revive ();
-        void traceroute (unsigned char *identity_, size_t identity_size_);
+        void traceroute (const blob_t &identity_);
 
         //  i_poll_events interface implementation.
         void in_event ();
diff --git a/src/zmq_init.cpp b/src/zmq_init.cpp
index f062ede3..9aebad05 100644
--- a/src/zmq_init.cpp
+++ b/src/zmq_init.cpp
@@ -72,15 +72,14 @@ bool zmq::zmq_init_t::write (::zmq_msg_t *msg_)
         return false;
 
     //  Retreieve the remote identity.
-    peer_identity.assign ((const char*) zmq_msg_data (msg_),
+    peer_identity.assign ((const unsigned char*) zmq_msg_data (msg_),
         zmq_msg_size (msg_));
     received = true;
 
     //  Once the initial handshaking is over, XREP sockets should start
     //  tracerouting individual messages.
     if (options.traceroute)
-        engine->traceroute ((unsigned char*) peer_identity.data (),
-            peer_identity.size ());
+        engine->traceroute (peer_identity);
 
     return true;
 }
@@ -164,14 +163,11 @@ void zmq::zmq_init_t::finalise ()
         //  If the peer has a unique name, find the associated session. If it
         //  doesn't exist, create it.
         else if (!peer_identity.empty ()) {
-            session = owner->find_session (
-                (unsigned char) peer_identity.size (),
-                (unsigned char*) peer_identity.data ());
+            session = owner->find_session (peer_identity);
             if (!session) {
                 session = new (std::nothrow) session_t (
                     choose_io_thread (options.affinity), owner, options,
-                    (unsigned char) peer_identity.size (),
-                    (unsigned char*) peer_identity.c_str ());
+                    peer_identity);
                 zmq_assert (session);
                 send_plug (session);
                 send_own (owner, session);
@@ -185,7 +181,7 @@ void zmq::zmq_init_t::finalise ()
         //  transient session.
         else {
             session = new (std::nothrow) session_t (
-                choose_io_thread (options.affinity), owner, options, 0, NULL);
+                choose_io_thread (options.affinity), owner, options, blob_t ());
             zmq_assert (session);
             send_plug (session);
             send_own (owner, session);
@@ -195,8 +191,7 @@ void zmq::zmq_init_t::finalise ()
         }
 
         //  No need to increment seqnum as it was already incremented above.
-        send_attach (session, engine, (unsigned char) peer_identity.size (),
-            (unsigned char*) peer_identity.data (), false);
+        send_attach (session, engine, peer_identity, false);
 
         //  Destroy the init object.
         engine = NULL;
diff --git a/src/zmq_init.hpp b/src/zmq_init.hpp
index df14293c..6f935c25 100644
--- a/src/zmq_init.hpp
+++ b/src/zmq_init.hpp
@@ -20,8 +20,6 @@
 #ifndef __ZMQ_ZMQ_INIT_HPP_INCLUDED__
 #define __ZMQ_ZMQ_INIT_HPP_INCLUDED__
 
-#include <string>
-
 #include "i_inout.hpp"
 #include "i_engine.hpp"
 #include "owned.hpp"
@@ -29,6 +27,7 @@
 #include "stdint.hpp"
 #include "options.hpp"
 #include "stdint.hpp"
+#include "blob.hpp"
 
 namespace zmq
 {
@@ -72,7 +71,7 @@ namespace zmq
         bool received;
 
         //  Identity of the peer socket.
-        std::string peer_identity;
+        blob_t peer_identity;
 
         //  TCP connecter creates session before the name of the peer is known.
         //  Thus we know only its ordinal number.