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

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

AES-128 encryption protects streams using Wowza CDN on Fastly targets by requiring devices to provide a matching key before a stream can be played. Wowza Video uses the external method of AES-128 encryption. When you use the external method, encryption keys are delivered to devices from an external URL.

Configure AES-128 encryption

1. Create a live stream. 
2. Go to Live streams in the navigation.
3. Select the live stream.
4. Click the Components tab.
5. In the Transcoder section at the top, click Configure.
6. Click the Properties tab.
7. Under Cupertino, in the AES 128 Host field, enter the URL the device will use to fetch the key to decrypt the stream.
8. Under Cupertino, in the AES 128 Secret field, 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 AES 128 Host.
9. Click Save Changes.

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