diff --git a/erlang/LICENSE b/erlang/LICENSE
new file mode 100644
index 00000000..7bcf85d0
--- /dev/null
+++ b/erlang/LICENSE
@@ -0,0 +1,16 @@
+License (GNU General Public License):
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+
+This program 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+USA
diff --git a/erlang/README.md b/erlang/README.md
new file mode 100644
index 00000000..3aeb88e7
--- /dev/null
+++ b/erlang/README.md
@@ -0,0 +1,22 @@
+fwknop
+=====
+
+Experimental native erlang fwknop client with Rijndael support.
+
+Build
+-----
+
+    $ rebar3 compile
+    $ rebar3 eunit
+
+Usage
+-----
+  
+    $ rebar3 shell
+    1> fwknop:knock("spaserver.domain.com", 62201, "Sz80RjpXOlhH2olGuKBUamHKcqyMBsS9BTgLaMugUsg=", "c0TOaMJ2aVPdYTh4Aa25Dwxni7PrLo2zLAtBoVwSepkvH6nLcW45Cjb9zaEC2SQd03kaaV+Ckx3FhCh5ohNM5Q==", { tcp, "1.1.1.1", 22 } ).
+    =INFO REPORT==== 15-Nov-2016::15:49:16 ===
+    Message: 0428888364523312:bXMxNzg0:1479224956:2.0.2:1:MTI3LjAuMC4xLHRjcC84NDQz
+    =INFO REPORT==== 15-Nov-2016::15:49:16 ===
+    HMAC:   KDZrTwZ+gFpqgzk8+BCXvYhRCxCzk084UyNzhihiWLU
+    ok
+    2>
diff --git a/erlang/rebar.config b/erlang/rebar.config
new file mode 100644
index 00000000..b22e2496
--- /dev/null
+++ b/erlang/rebar.config
@@ -0,0 +1,5 @@
+{erl_opts, [debug_info]}.
+{deps,	[
+	{pkcs7, {git, "https://github.com/camshaft/pkcs7.erl"}}
+	]
+}.
diff --git a/erlang/rebar.lock b/erlang/rebar.lock
new file mode 100644
index 00000000..b08e059d
--- /dev/null
+++ b/erlang/rebar.lock
@@ -0,0 +1,4 @@
+[{<<"pkcs7">>,
+  {git,"https://github.com/camshaft/pkcs7.erl",
+       {ref,"00218999ce9b60848aa1f36612248d1079c7ef06"}},
+  0}].
diff --git a/erlang/src/fwknop.app.src b/erlang/src/fwknop.app.src
new file mode 100644
index 00000000..2dd203b4
--- /dev/null
+++ b/erlang/src/fwknop.app.src
@@ -0,0 +1,16 @@
+{application, fwknop,
+ [{description, "An OTP application"},
+  {vsn, "0.1.0"},
+  {registered, []},
+  {mod, { fwknop_app, []}},
+  {applications,
+   [kernel,
+    stdlib
+   ]},
+  {env,[]},
+  {modules, []},
+
+  {maintainers, []},
+  {licenses, []},
+  {links, []}
+ ]}.
diff --git a/erlang/src/fwknop.erl b/erlang/src/fwknop.erl
new file mode 100644
index 00000000..5c353689
--- /dev/null
+++ b/erlang/src/fwknop.erl
@@ -0,0 +1,85 @@
+%%  License (GNU General Public License):
+%%
+%%  This program is free software; you can redistribute it and/or
+%%  modify it under the terms of the GNU General Public License
+%%  as published by the Free Software Foundation; either version 2
+%%  of the License, or (at your option) any later version.
+%%
+%%  This program 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 General Public License for more details.
+%%
+%%  You should have received a copy of the GNU General Public License
+%%  along with this program; if not, write to the Free Software
+%%  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+%%  USA
+
+-module( fwknop ).
+-compile( export_all ).
+
+-define( FwknopVersion, "2.0.2" ).
+-define( CommandMode, 0 ).
+-define( AccessMode, 1 ).
+
+-import( lists,	[ dropwhile/2, nth/2, reverse/1, seq/2, split/2 ] ).
+-import( pkcs7, [ pad/1 ] ).
+
+packet( Proto, Ip, Port, RijndaelKeyB64, HmacKeyB64 ) ->
+	E64 = fun( Bin ) -> base64:encode( Bin ) end,
+
+	RijndaelKey	= base64:decode( RijndaelKeyB64 ),
+	HmacKey		= base64:decode( HmacKeyB64 ),
+
+	Rand		= random_digits( 16 ),
+	User		= E64( os:getenv( "USER" ) ),
+	Version		= ?FwknopVersion,
+	MsgType		= integer_to_list( ?AccessMode ),
+	Request		= strip_base64(E64( list_to_binary( io_lib:format( "~s,~s/~b", [ Ip, Proto, Port ] ) ) ) ),
+	Time 		= timestamp(),
+
+	Message		= list_to_binary( io_lib:format( "~s:~s:~p:~s:~s:~s", [ Rand, User, Time, Version, MsgType, Request ] ) ),
+	error_logger:info_msg( "Message: ~s~n", [ Message ] ),
+	Digest		= strip_base64( E64( crypto:hash( sha256, Message ) ) ),
+
+	Plaintext	= pkcs7:pad( <<Message/binary, <<":">>/binary, Digest/binary>> ),
+	Salt 		= crypto:strong_rand_bytes( 8 ),
+	
+	{Key, IV} 	= pbkdf1( Salt, RijndaelKey ),
+	Magic		= <<"Salted__">>,
+
+	Ciphertext 	= crypto:block_encrypt( aes_cbc256, Key, IV, Plaintext ),
+	SpaData		= strip_base64( E64( <<Magic/binary, Salt/binary, Ciphertext/binary>> ) ),
+
+	Hmac		= strip_base64( E64( crypto:hmac( sha256, HmacKey, SpaData ) ) ),
+	error_logger:info_msg( "HMAC:   ~s~n", [ Hmac ] ),
+
+	% strip encoded magic word
+	SpaData2 = binary:part(SpaData, {10, size(SpaData) - 10} ),
+	
+	<< SpaData2/binary,  Hmac/binary>>.
+
+%
+%	miscellaneous utilities
+%
+pbkdf1( Salt, Key ) ->
+	Round1 = erlang:md5( <<Key/binary, Salt/binary>> ),
+	Round2 = erlang:md5( <<Round1/binary, Key/binary, Salt/binary>> ),
+	Round3 = erlang:md5( <<Round2/binary, Key/binary, Salt/binary>> ),
+	{ <<Round1/binary, Round2/binary>>, <<Round3/binary>> }.
+		
+strip_base64( Bin ) ->
+	F = fun( C ) -> C == $= end,
+	list_to_binary( reverse( dropwhile( F, reverse( binary_to_list( Bin ) ) ) ) ).
+
+random_digits( N ) ->
+	list_to_binary( [ nth( crypto:rand_uniform( 1, 10 ), "0123456789" ) || _ <- seq( 1, N ) ] ).
+
+timestamp() ->
+	{ A, B, _ }	= os:timestamp(),
+	list_to_integer( integer_to_list( (A * 1000000) + B ) ).
+
+knock( Host, Port, RijndaelKeyB64, HmacKeyB64, { Proto, SrcIp, DstPort } ) ->
+	Packet = packet( Proto, SrcIp, DstPort, RijndaelKeyB64, HmacKeyB64 ),
+	{ ok, Socket } = gen_udp:open( 0, [binary] ),
+	gen_udp:send( Socket, Host, Port, Packet ).
diff --git a/erlang/src/fwknop_tests.erl b/erlang/src/fwknop_tests.erl
new file mode 100644
index 00000000..7189b854
--- /dev/null
+++ b/erlang/src/fwknop_tests.erl
@@ -0,0 +1,38 @@
+%%  License (GNU General Public License):
+%%
+%%  This program is free software; you can redistribute it and/or
+%%  modify it under the terms of the GNU General Public License
+%%  as published by the Free Software Foundation; either version 2
+%%  of the License, or (at your option) any later version.
+%%
+%%  This program 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 General Public License for more details.
+%%
+%%  You should have received a copy of the GNU General Public License
+%%  along with this program; if not, write to the Free Software
+%%  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+%%  USA
+
+-module( fwknop_tests ).
+
+-include_lib("eunit/include/eunit.hrl").
+
+pbkdf1_test() ->
+	Salt		= <<0,0,0,0,0,0,0,0>>,
+	RijndaelKey	= base64:decode("Sz80RjpXOlhH2olGuKBUamHKcqyMBsS9BTgLaMugUsg="),
+
+	ExpectedKey	= <<80,137,195,6,117,8,63,199,226,93,78,205,231,238,241,80,217,161,149,164,60,102,129,175,81,53,82,23,137,50,236,37>>,
+	ExpectedIV	= <<56,251,47,154,60,96,84,106,192,163,161,216,59,202,166,203>>,
+
+	{ExpectedKey, ExpectedIV} = fwknop:pbkdf1(Salt, RijndaelKey).
+
+strip_base64_test() ->
+	Encoded		= base64:encode( "Salted" ),
+	Encoded2	= base64:encode( "Salted_" ),
+	Encoded3	= base64:encode( "Salted__" ),
+
+	<< "U2FsdGVk" >>	= fwknop:strip_base64(Encoded),
+	<< "U2FsdGVkXw" >>	= fwknop:strip_base64(Encoded2),
+	<< "U2FsdGVkX18" >>	= fwknop:strip_base64(Encoded3).