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An alternative implementation of Erlang TCP/TLS layer.

etls is a NIF-based implementation of the whole TLS stack, built on top of Asio and BoringSSL. It manages its own native threads to asynchronously handle socket operations.

The main (and very important) benefit of using this project instead of Erlang's built-in ssl is hardware acceleration. etls module achieves an order of magnitude higher bandwidth when encoding/decoding data.

Currently only TLSv1.2 is supported.


Benchmark ran on OS X 10.11.5, 2,2 GHz Intel Core i7 (4 cores with HT). The benchmark consisted of 10 concurrent connections, each sending 10 messages, each of size 100 MB for a total of 1 GB per connection. The bandwidth has been calculated using time measured between the first message sent and the last message received.

OTP version transport bandwidth
18.3 ssl 70 MB/s
19.0-rc1 ssl 111 MB/s
19.0-rc1 etls 833 MB/s



  • cmake >= 3.1.0
  • erlang >= 17.0
  • g++ >= 4.9.0 (or clang)
  • perl
  • make
  • openssl

Most of those dependencies are probably already present on your system. For example to install all needed dependencies on Ubuntu 16.10, you only need to run apt-get install build-essentials cmake erlang. Builds can be also sped up by installing ninja-build - etls will make use of it automatically while building.

Once you have all of the dependencies, simply run make in etls directory to build it.

User Guide

Add etls as a rebar dependency to your project:

{deps, [
  {etls, "1.1.2", {git, "", {tag, "1.1.2"}}}

You can also take advantage of the package.

Now you can use etls module much like you would use ssl:

% Server side

{ok, ListenSocket} =
  etls:listen(9999, [{certfile, "cert.pem"}, {keyfile, "key.pem"},
                     {reuseaddr, true}]),

{ok, Socket} = etls:accept(ListenSocket),
etls:setopts(Socket, [{active, once}]),

receive AMessage -> io:format("~p~n", [AMessage]) end.
% Client side

{ok, Socket} = etls:connect("localhost", 9999,  [], infinity),
etls:send(Socket, "foo").

Using with Ranch

etls can be easily used with Ranch by starting a listener with ranch_etls as the transport module:

{ok, _} = ranch:start_listener(tcp_echo, 100,
                               ranch_etls, [{port, 5555}, {certfile, CertPath}],
                               echo_protocol, []).


API documentation can be found at

Implemented ssl functions

The following ssl/inet functions are currently implemented:

  • connect/3
  • connect/4
  • send/2
  • recv/2
  • recv/3
  • listen/2
  • accept/1 (ssl: transport_accept/1)
  • accept/2 (ssl: transport_accept/2)
  • handshake/1 (ssl: accept/1)
  • handshake/2 (ssl: accept/2)
  • setopts/2
  • controlling_process/2
  • peername/1
  • sockname/1
  • close/1
  • peercert/1
  • certificate_chain/1 (not present in ssl)
  • shutdown/2

Implemented ssl options

The following ssl/inet options are currently supported:

  • {packet, raw | 0 | 1 | 2 | 4}
  • {active, boolean() | once}
  • {exit_on_close, boolean()}
  • {verify_type, verify_none | verify_peer}
  • {fail_if_no_peer_cert, boolean()}
  • {verify_client_once, boolean()}
  • {rfc2818_verification_hostname, str()}
  • {cacerts, [pem_encoded()]}
  • {crls, [pem_encoded()]}
  • {certfile, str()}
  • {keyfile, str()}
  • {chain, [pem_encoded()]}