Secure HLS streams with AES-128 external encryption in Wowza Video Legacy

The Wowza Video™ service allows you to secure HLS streams using the external method of AES-128 encryption. When you use the external method of AES-128 encryption, encryption keys are delivered to devices from an external URL. This article describes how to use the Wowza Video user interface to configure AES-128 encryption for an HLS stream.

Configure AES-128 encryption

1. Do one of the following:
   • Under Advanced on the left navigation bar, click Transcoders, and then click Add Transcoder. Complete the steps to finish adding the transcoder. For more information, see Create and manage transcoders in Wowza Video.
   • Under Advanced on the left navigation bar, click Transcoders, and then select a transcoder on the Transcoders page.
      

     Note: Transcoders created through the live stream workflow appear as [Live stream name] / Transcoder.

2. Click the Properties tab and then click Edit.
3. Under HLS, select Enabled for HLS AES128 Host and enter the URL that devices will use to fetch the key to decrypt the stream.
4. Under HLS, select Enabled for HLS AES128 Secret and enter a 16-byte key that will be used to decrypt the stream. The key must be 32 characters in length and can only contain hex characters (a-f, A-F, 0-9). The key must match the key returned by the HLS AES128 Host.
5. Click Save.

Examples

The following examples show how to use popular web application technologies such as ASP.NET, JSP, and PHP to send the key data. Each example includes a Boolean isValid value that defaults to true. You can modify the examples to provide your own security tests to validate that users can access the content. If users shouldn't be allowed to access the content, you can block them from receiving the decryption key by setting isValid to false.

If the request for the key returns a status of 403, then the device won't be able to decrypt and play the stream. If the key is returned, then the stream will be decrypted and played. Require HTTPS access to this key to ensure that it isn't sent over an unsecured connection on the Internet.

The key being sent in these examples is DE51A7254739C0EDF1DCE13BBB308FF0. You should substitute this value with a different 16-byte key. The key should match the key entered in the HLS AES128 Secret field on the transcoder Properties tab.

ASP.NET example

<%@ Page Language="C#" %>
<%

    Boolean isValid = true;
    if (!isValid)
    {
        Response.Status = "403 Forbidden";
    }
    else
    {
        Response.AddHeader("Content-Type", "binary/octet-stream");
        Response.AddHeader("Pragma", "nocache");

        String keyStr = "DE51A7254739C0EDF1DCE13BBB308FF0";

        int len = keyStr.Length/2;
        byte[] keyBuffer = new byte[len];

        for (int i=0;i<len;i++)
            keyBuffer[i] = Convert.ToByte(keyStr.Substring(i*2, 2), 16);

        Response.BinaryWrite(keyBuffer);
        Response.Flush();
        Response.End();
    }

%>

JSP example

<%@ page import="java.util.*,java.io.*" %>
<%

boolean isValid = true;
if (!isValid)
{
response.setStatus( 403 ); 
}
else
{
response.setHeader("Content-Type", "binary/octet-stream");
response.setHeader("Pragma", "no-cache");

String keyStr = "DE51A7254739C0EDF1DCE13BBB308FF0";

int len = keyStr.length()/2;
byte[] keyBuffer = new byte[len];

for (int i=0;i<len;i++)
keyBuffer[i] = (byte)Integer.parseInt(keyStr.substring(i*2, (i*2)+2), 16);

OutputStream outs = response.getOutputStream();
outs.write(keyBuffer);
outs.flush();
}

%>

PHP example

<?php

// Check if function exists (php5.4+ includes this method)
if(!function_exists("hex2bin")){
function hex2bin($h)
{
if (!is_string($h))
return null;
$r = '';
for ($a=0;$a<strlen($h);$a+=2)
{
$r .= chr(hexdec($h{$a}.$h{($a+1)}));
}
return $r;
}
}

$isValid = true;
if (! $isValid)
{
header('HTTP/1.0 403 Forbidden');
}
else
{
header('Content-Type: binary/octet-stream');
header('Pragma: no-cache');


echo hex2bin('DE51A7254739C0EDF1DCE13BBB308FF0');

exit(); // this is needed to ensure cr/lf is not added to output
}

?>

More resources

• Test AES encryption for HLS streams from Wowza Video