diff --git a/src/Makefile.am b/src/Makefile.am
index 530af01e..b3e9d166 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -51,6 +51,7 @@ libzmq_la_SOURCES = \
     pgm_sender.hpp \
     pgm_socket.hpp \
     pipe.hpp \
+    plain_mechanism.hpp \
     platform.hpp \
     poll.hpp \
     poller.hpp \
@@ -114,6 +115,7 @@ libzmq_la_SOURCES = \
     pgm_sender.cpp \
     pgm_socket.cpp \
     pipe.cpp \
+    plain_mechanism.cpp \
     poll.cpp \
     poller_base.cpp \
     pull.cpp \
diff --git a/src/ipc_connecter.cpp b/src/ipc_connecter.cpp
index 716fef0f..30841cd1 100644
--- a/src/ipc_connecter.cpp
+++ b/src/ipc_connecter.cpp
@@ -112,7 +112,8 @@ void zmq::ipc_connecter_t::out_event ()
         return;
     }
     //  Create the engine object for this connection.
-    stream_engine_t *engine = new (std::nothrow) stream_engine_t (fd, options, endpoint);
+    stream_engine_t *engine = new (std::nothrow)
+        stream_engine_t (fd, options, false, endpoint);
     alloc_assert (engine);
 
     //  Attach the engine to the corresponding session object.
diff --git a/src/ipc_listener.cpp b/src/ipc_listener.cpp
index b3ad88bc..d503d73e 100644
--- a/src/ipc_listener.cpp
+++ b/src/ipc_listener.cpp
@@ -80,7 +80,8 @@ void zmq::ipc_listener_t::in_event ()
     }
 
     //  Create the engine object for this connection.
-    stream_engine_t *engine = new (std::nothrow) stream_engine_t (fd, options, endpoint);
+    stream_engine_t *engine = new (std::nothrow)
+        stream_engine_t (fd, options, true, endpoint);
     alloc_assert (engine);
 
     //  Choose I/O thread to run connecter in. Given that we are already
diff --git a/src/plain_mechanism.cpp b/src/plain_mechanism.cpp
new file mode 100644
index 00000000..d235dfa9
--- /dev/null
+++ b/src/plain_mechanism.cpp
@@ -0,0 +1,359 @@
+/*
+    Copyright (c) 2007-2013 Contributors as noted in the AUTHORS file
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser 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
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "platform.hpp"
+#ifdef ZMQ_HAVE_WINDOWS
+#include "windows.hpp"
+#endif
+
+#include <string.h>
+#include <string>
+
+#include "msg.hpp"
+#include "err.hpp"
+#include "plain_mechanism.hpp"
+#include "wire.hpp"
+
+zmq::plain_mechanism_t::plain_mechanism_t (const options_t &options_,
+                                           bool as_server_) :
+    mechanism_t (options_),
+    state (as_server_? waiting_for_hello: sending_hello)
+{
+}
+
+zmq::plain_mechanism_t::~plain_mechanism_t ()
+{
+}
+
+int zmq::plain_mechanism_t::next_handshake_message (msg_t *msg_)
+{
+    int rc = 0;
+
+    switch (state) {
+    case sending_hello:
+        rc = hello_command (msg_);
+        if (rc == 0)
+            state = waiting_for_welcome;
+        break;
+    case sending_welcome:
+        rc = welcome_command (msg_);
+        if (rc == 0)
+            state = waiting_for_initiate;
+        break;
+    case sending_initiate:
+        rc = initiate_command (msg_);
+        if (rc == 0)
+            state = waiting_for_ready;
+        break;
+    case sending_ready:
+        rc = ready_command (msg_);
+        if (rc == 0)
+            state = ready;
+        break;
+    default:
+        errno = EAGAIN;
+        rc = -1;
+    }
+
+    return rc;
+}
+
+int zmq::plain_mechanism_t::process_handshake_message (msg_t *msg_)
+{
+    int rc = 0;
+
+    switch (state) {
+    case waiting_for_hello:
+        rc = process_hello_command (msg_);
+        if (rc == 0)
+            state = sending_welcome;
+        break;
+    case waiting_for_welcome:
+        rc = process_welcome_command (msg_);
+        if (rc == 0)
+            state = sending_initiate;
+        break;
+    case waiting_for_initiate:
+        rc = process_initiate_command (msg_);
+        if (rc == 0)
+            state = sending_ready;
+        break;
+    case waiting_for_ready:
+        rc = process_ready_command (msg_);
+        if (rc == 0)
+            state = ready;
+        break;
+    default:
+        errno = EAGAIN;
+        rc = -1;
+    }
+
+    if (rc == 0) {
+        rc = msg_->close ();
+        errno_assert (rc == 0);
+        rc = msg_->init ();
+        errno_assert (rc == 0);
+    }
+
+    return 0;
+}
+
+bool zmq::plain_mechanism_t::is_handshake_complete () const
+{
+    return state == ready;
+}
+
+int zmq::plain_mechanism_t::hello_command (msg_t *msg_) const
+{
+    //  TODO: fetch these from options
+    const std::string username = "username";
+    const std::string password = "password";
+
+    zmq_assert (username.length () < 256);
+    zmq_assert (password.length () < 256);
+
+    const size_t command_size = 8 + 1 + username.length () +
+        1 + password.length ();
+
+    const int rc = msg_->init_size (command_size);
+    errno_assert (rc == 0);
+
+    unsigned char *ptr = static_cast<unsigned char*> (msg_->data ());
+
+    memcpy (ptr, "HELLO   ", 8);
+    ptr += 8;
+    *ptr++ = static_cast <unsigned char> (username.length ());
+    memcpy (ptr, username.c_str (), username.length ());
+    ptr += username.length ();
+    *ptr++ = static_cast <unsigned char> (password.length ());
+    memcpy (ptr, password.c_str (), password.length ());
+    ptr += password.length ();
+
+    // TODO: check username and password
+
+    return 0;
+}
+
+int zmq::plain_mechanism_t::process_hello_command (msg_t *msg_)
+{
+    const unsigned char *ptr = static_cast <unsigned char *> (msg_->data ());
+    size_t bytes_left = msg_->size ();
+
+    if (bytes_left < 8 || memcmp (ptr, "HELLO   ", 8)) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    ptr += 8;
+    bytes_left -= 8;
+
+    if (bytes_left < 1) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    size_t username_length = static_cast <size_t> (*ptr++);
+    bytes_left -= 1;
+
+    if (bytes_left < username_length) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    const std::string username = std::string ((char *) ptr, username_length);
+    ptr += username_length;
+    bytes_left -= username_length;
+
+    if (bytes_left < 1) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    size_t password_length = static_cast <size_t> (*ptr++);
+    bytes_left -= 1;
+
+    if (bytes_left < password_length) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    const std::string password = std::string ((char *) ptr, password_length);
+    ptr += password_length;
+    bytes_left -= password_length;
+
+    if (bytes_left > 0) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    return 0;
+}
+
+int zmq::plain_mechanism_t::welcome_command (msg_t *msg_) const
+{
+    const int rc = msg_->init_size (8);
+    errno_assert (rc == 0);
+    memcpy (msg_->data (), "WELCOME ", 8);
+    return 0;
+}
+
+int zmq::plain_mechanism_t::process_welcome_command (msg_t *msg_)
+{
+    const unsigned char *ptr = static_cast <unsigned char *> (msg_->data ());
+    size_t bytes_left = msg_->size ();
+
+    if (bytes_left != 8 ||  memcmp (ptr, "WELCOME ", 8)) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    return 0;
+}
+
+int zmq::plain_mechanism_t::initiate_command (msg_t *msg_) const
+{
+    unsigned char * const command_buffer = (unsigned char *) malloc (512);
+    alloc_assert (command_buffer);
+
+    unsigned char *ptr = command_buffer;
+
+    //  Add mechanism string
+    memcpy (ptr, "INITIATE", 8);
+    ptr += 8;
+
+    //  Add socket type property
+    const char *socket_type = socket_type_string (options.type);
+    ptr += add_property (ptr, "Socket-Type", socket_type, strlen (socket_type));
+
+    //  Add identity property
+    if (options.type == ZMQ_REQ
+    ||  options.type == ZMQ_DEALER
+    ||  options.type == ZMQ_ROUTER) {
+        ptr += add_property (ptr, "Identity",
+            options.identity, options.identity_size);
+    }
+
+    const size_t command_size = ptr - command_buffer;
+    const int rc = msg_->init_size (command_size);
+    errno_assert (rc == 0);
+    memcpy (msg_->data (), command_buffer, command_size);
+    free (command_buffer);
+
+    return 0;
+}
+
+int zmq::plain_mechanism_t::process_initiate_command (msg_t *msg_)
+{
+    const unsigned char *ptr = static_cast <unsigned char *> (msg_->data ());
+    size_t bytes_left = msg_->size ();
+
+    if (bytes_left < 8 || memcmp (ptr, "INITIATE", 8)) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    return parse_property_list (ptr + 8, bytes_left - 8);
+}
+
+int zmq::plain_mechanism_t::ready_command (msg_t *msg_) const
+{
+    unsigned char * const command_buffer = (unsigned char *) malloc (512);
+    alloc_assert (command_buffer);
+
+    unsigned char *ptr = command_buffer;
+
+    //  Add mechanism string
+    memcpy (ptr, "READY   ", 8);
+    ptr += 8;
+
+    //  Add socket type property
+    const char *socket_type = socket_type_string (options.type);
+    ptr += add_property (ptr, "Socket-Type", socket_type, strlen (socket_type));
+
+    //  Add identity property
+    if (options.type == ZMQ_REQ
+    ||  options.type == ZMQ_DEALER
+    ||  options.type == ZMQ_ROUTER) {
+        ptr += add_property (ptr, "Identity",
+            options.identity, options.identity_size);
+    }
+
+    const size_t command_size = ptr - command_buffer;
+    const int rc = msg_->init_size (command_size);
+    errno_assert (rc == 0);
+    memcpy (msg_->data (), command_buffer, command_size);
+    free (command_buffer);
+
+    return 0;
+}
+
+int zmq::plain_mechanism_t::process_ready_command (msg_t *msg_)
+{
+    const unsigned char *ptr = static_cast <unsigned char *> (msg_->data ());
+    size_t bytes_left = msg_->size ();
+
+    if (bytes_left < 8 || memcmp (ptr, "READY   ", 8)) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    return parse_property_list (ptr + 8, bytes_left - 8);
+}
+
+int zmq::plain_mechanism_t::parse_property_list (const unsigned char *ptr,
+    size_t bytes_left)
+{
+    while (bytes_left > 1) {
+        const size_t name_length = static_cast <size_t> (*ptr);
+        ptr += 1;
+        bytes_left -= 1;
+
+        if (bytes_left < name_length)
+            break;
+        const std::string name = std::string((const char *) ptr, name_length);
+        ptr += name_length;
+        bytes_left -= name_length;
+
+        if (bytes_left < 4)
+            break;
+        const size_t value_length = static_cast <size_t> (get_uint32 (ptr));
+        ptr += 4;
+        bytes_left -= 4;
+
+        if (bytes_left < value_length)
+            break;
+        const unsigned char * const value = ptr;
+        ptr += value_length;
+        bytes_left -= value_length;
+
+        if (name == "Socket-Type") {
+            //  TODO: Implement socket type checking
+        }
+        else
+        if (name == "Identity" && options.recv_identity)
+            set_peer_identity (value, value_length);
+    }
+
+    if (bytes_left > 0) {
+        errno = EPROTO;
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/src/plain_mechanism.hpp b/src/plain_mechanism.hpp
new file mode 100644
index 00000000..a89d0a41
--- /dev/null
+++ b/src/plain_mechanism.hpp
@@ -0,0 +1,74 @@
+/*
+    Copyright (c) 2007-2013 Contributors as noted in the AUTHORS file
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser 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
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZMQ_PLAIN_MECHANISM_HPP_INCLUDED__
+#define __ZMQ_PLAIN_MECHANISM_HPP_INCLUDED__
+
+#include "mechanism.hpp"
+#include "options.hpp"
+
+namespace zmq
+{
+
+    class msg_t;
+
+    class plain_mechanism_t : public mechanism_t
+    {
+    public:
+
+        plain_mechanism_t (const options_t &options_, bool as_server_);
+        virtual ~plain_mechanism_t ();
+
+        // mechanism implementation
+        virtual int next_handshake_message (msg_t *msg_);
+        virtual int process_handshake_message (msg_t *msg_);
+        virtual bool is_handshake_complete () const;
+
+    private:
+
+        enum state_t {
+            sending_hello,
+            waiting_for_hello,
+            sending_welcome,
+            waiting_for_welcome,
+            sending_initiate,
+            waiting_for_initiate,
+            sending_ready,
+            waiting_for_ready,
+            ready
+        };
+
+        state_t state;
+
+        int hello_command (msg_t *msg_) const;
+        int welcome_command (msg_t *msg_) const;
+        int initiate_command (msg_t *msg_) const;
+        int ready_command (msg_t *msg_) const;
+
+        int process_hello_command (msg_t *msg_);
+        int process_welcome_command (msg_t *msg);
+        int process_ready_command (msg_t *msg_);
+        int process_initiate_command (msg_t *msg_);
+
+        int parse_property_list (const unsigned char *ptr, size_t length);
+    };
+
+}
+
+#endif
diff --git a/src/stream_engine.cpp b/src/stream_engine.cpp
index 6e4e69d1..4c604db8 100644
--- a/src/stream_engine.cpp
+++ b/src/stream_engine.cpp
@@ -41,6 +41,7 @@
 #include "v2_encoder.hpp"
 #include "v2_decoder.hpp"
 #include "null_mechanism.hpp"
+#include "plain_mechanism.hpp"
 #include "raw_decoder.hpp"
 #include "raw_encoder.hpp"
 #include "config.hpp"
@@ -49,8 +50,10 @@
 #include "likely.hpp"
 #include "wire.hpp"
 
-zmq::stream_engine_t::stream_engine_t (fd_t fd_, const options_t &options_, const std::string &endpoint_) :
+zmq::stream_engine_t::stream_engine_t (fd_t fd_, const options_t &options_,
+    bool as_server_, const std::string &endpoint_) :
     s (fd_),
+    as_server (as_server_),
     inpos (NULL),
     insize (0),
     decoder (NULL),
@@ -523,13 +526,19 @@ bool zmq::stream_engine_t::handshake ()
         if (memcmp (greeting_recv + 12, "NULL\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 20) == 0) {
             mechanism = new (std::nothrow) null_mechanism_t (options);
             alloc_assert (mechanism);
-            read_msg = &stream_engine_t::next_handshake_message;
-            write_msg = &stream_engine_t::process_handshake_message;
+        }
+        else
+        if (memcmp (greeting_recv + 12, "PLAIN\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 20) == 0) {
+            mechanism = new (std::nothrow) plain_mechanism_t (options, as_server);
+            alloc_assert (mechanism);
         }
         else {
             error ();
             return false;
         }
+
+        read_msg = &stream_engine_t::next_handshake_message;
+        write_msg = &stream_engine_t::process_handshake_message;
     }
 
     // Start polling for output if necessary.
diff --git a/src/stream_engine.hpp b/src/stream_engine.hpp
index 91d641b8..31acc83c 100644
--- a/src/stream_engine.hpp
+++ b/src/stream_engine.hpp
@@ -52,7 +52,8 @@ namespace zmq
     {
     public:
 
-        stream_engine_t (fd_t fd_, const options_t &options_, const std::string &endpoint);
+        stream_engine_t (fd_t fd_, const options_t &options_,
+            bool as_server_, const std::string &endpoint);
         ~stream_engine_t ();
 
         //  i_engine interface implementation.
@@ -112,6 +113,9 @@ namespace zmq
         //  Underlying socket.
         fd_t s;
 
+        //  True iff this is server's engine.
+        bool as_server;
+
         msg_t tx_msg;
 
         handle_t handle;
diff --git a/src/tcp_connecter.cpp b/src/tcp_connecter.cpp
index e1ddf617..b83854ce 100644
--- a/src/tcp_connecter.cpp
+++ b/src/tcp_connecter.cpp
@@ -125,7 +125,8 @@ void zmq::tcp_connecter_t::out_event ()
     tune_tcp_keepalives (fd, options.tcp_keepalive, options.tcp_keepalive_cnt, options.tcp_keepalive_idle, options.tcp_keepalive_intvl);
 
     //  Create the engine object for this connection.
-    stream_engine_t *engine = new (std::nothrow) stream_engine_t (fd, options, endpoint);
+    stream_engine_t *engine = new (std::nothrow)
+        stream_engine_t (fd, options, false, endpoint);
     alloc_assert (engine);
 
     //  Attach the engine to the corresponding session object.
diff --git a/src/tcp_listener.cpp b/src/tcp_listener.cpp
index 7de38cb1..a291f53c 100644
--- a/src/tcp_listener.cpp
+++ b/src/tcp_listener.cpp
@@ -91,7 +91,8 @@ void zmq::tcp_listener_t::in_event ()
     tune_tcp_keepalives (fd, options.tcp_keepalive, options.tcp_keepalive_cnt, options.tcp_keepalive_idle, options.tcp_keepalive_intvl);
 
     //  Create the engine object for this connection.
-    stream_engine_t *engine = new (std::nothrow) stream_engine_t (fd, options, endpoint);
+    stream_engine_t *engine = new (std::nothrow)
+        stream_engine_t (fd, options, true, endpoint);
     alloc_assert (engine);
 
     //  Choose I/O thread to run connecter in. Given that we are already