Content Protection for HTTP Live Streaming

ROGER PANTOS: Good morning, everyone.

Welcome to this year's Worldwide Developers Conference. This is your first real session.

So, welcome.

Today -- thank you.

Today we are going to be talking about a pretty exciting addition to HTTP Live Streaming.

You know, we are always looking at whatever it is that's preventing you guys from using HLS to deploy your content the way you want to, and content protection, which is to say allowing your users to watch your content, listen to your content without making unauthorized use of it, has always been a really difficult problem that a lot of you have had to sort of contend with.

And, as the bit rates get higher, and the resolutions get higher, those demands are only going to get louder.

And that's why I am extremely pleased, finally, to be able to announce today FairPlay Streaming.

So what is it? First and foremost, it is our best content protection technology, packaged in a way that allows you to use it to protect your HLS content.

Now, it is not new.

We have been working for the past three years with some of our major content partners to help them deploy FairPlay Streaming in their apps and on Apple TV.

And at this point, it has been used to protect a lot of content, including some of the most popular movies and television shows in the world.

Now, you can use it on iOS, on Apple TV, and on OS X.

Of course, on our mobile devices, battery life is king. And so, when we designed FairPlay Streaming, every choice we made was predicated on giving you good battery life. The codecs we chose, the encryption we chose, how we implemented it, even the hardware we took advantage of. And, so, you get great security, but you also get great battery life. And it is also integrated with AirPlay, seamlessly.

And, so, with full protection.

Now, you may be saying, okay, well, that sounds pretty good, but I've got a lot of content. I mean, is Apple -- how is Apple going to make me pay for this FairPlay Streaming thing? Is going to be like a per movie charge, per playback, as a flat rate? We went back and forth on that, and we eventually did settle on a flat rate.

Zero. If you guys are paying your 99-dollar a year developer fee to us, you will not need to pay Apple a penny more to use FairPlay Streaming as much as you want.

So, now, at this point, any marketing folks in the audience are like: Oh, that sounds awesome! And the engineer sitting next to you is like: No, no, really, what is it? Okay. So, it is really very simple.

What we did is, we attacked the most essential building block of a DRM system, which is key protection.

And so FairPlay Streaming is essentially and really only a secure key delivery system. It's a way to transfer the keys from your server on the Internet to the device, and use it on that device without allowing it to be obtained by an attacker so they can decrypt your content.

We designed it to be easy to use and also easy to adopt. We recognized that a lot of you, particularly if you are streaming premium content or subscription content, you are already talking to some kind of secure back end.

And so we designed FairPlay Streaming so that the delivery part is agnostic, the protocol you're using. If you have got a secure connection, you can adopt FairPlay Streaming extremely easily. And if you don't, you can just use HTTPS. It's a great choice.

Finally, a lot of folks have asked me about HDCP in the past. With FairPlay Streaming is the answer to this.

If your device is connected to a television or another external input, it must be HDMI, and HDCP must be active or any FairPlay Streaming content playback will fail, no exceptions.

Now, when we designed it, we knew that there's a lot of difference, business rules and logic, and everybody has their own flavor. And so we didn't want to build a big, complicated thing and force you into our box. So we built just the key delivery mechanism. We didn't build a big rights expression language evaluator or create a long list of policies that you need to adhere to.

And that means that if your business logic requires those things, you are in control. You are still the gate keeper. So, once you give the media stack a FairPlay Streaming key, we will play it. No questions asked. We will protect the key, we'll go and play it.

And so, if you need to do some policy enforcement or user authentication or per device slot management, then you can do that on top of FairPlay Streaming. And so again, it goes into being easy to integrate.

So now let's talk about some concrete steps. That's kind of what FairPlay Streaming gives you. Let's talk about the steps that you need to do to adopt it.

Basically there are three steps.

The first one and probably the largest one is because FairPlay Streaming is an online key delivery protocol, you must be online to get your key, and once the playback stops, the key goes poof.

You need to integrate what we call a key security module into your key server.

And so that's the biggest step, and we'll go into a lot of detail about that in a second.

But the second thing is, then you need to add a little bit of code to your application, called an AV asset resource loader delegate.

And that code is going to be responsible for relaying the key requests from AV foundation to your back end, and then returning the response from your back end back to AV foundation.

Then finally what you need to do is, prepare your content. And that means you need to encrypt it, using the AES Sample encryption. This is the format that we introduced, oh, three years ago, coincidentally. And so, rather than the traditional bulk entire segment encryption that HLS is using originally, this just encrypts small slices of each sample and it ensures that we can drive the decryption down to the lowest level of the system.

And so you need to pick a content key, store that away in your back end database, encrypt your content, and then put a reference to that key into your playlist so that when you your little bit of code receives a request for that key it knows which one to ask your back end for. And so what I would like to do next is have us go into greater detail on all three of those steps. And to do that, I would like to introduce a colleague of mine who works on the FairPlay team, Gianpaolo Fasoli. Welcome.

GIANPAOLO FASOLI: Thank you, Roger.

Good morning, everyone. My name's Gianpaolo Fasoli, and I am a FairPlay Streaming Engineer at Apple.

So, with Roger's overview in mind, I'd like to talk to you about what it takes to design a FairPlay Streaming system. And the first thing I'm going to talk about is the purpose and the importance of what we refer to as the FairPlay Streaming credentials. Next up, I'm going to identify the actors in the system and the data flows. Then I'm going to talk about what Apple provides in the things that you are going to build and in the things that you are going to build, we're going to start by talking about the server side and how to integrate the key security module that Roger was talking about into your key server. We're going to talk about how to test that integration. We're going to move on to the client side and how to integrate FairPlay Streaming into your application, and then we're also going to be talking about the updates you are going to be making to your content authoring workflow, in order to encrypt that content and verify the changes that you are making to your workflow.

So when we talk about FairPlay Streaming credentials, the reason we have those is so that we can differentiate your FairPlay Streaming deployment from other FPS deployments out there. And the reason they are required is because you need them so that your customers can actually play their content on the customer devices.

For those reasons, it is critical that you protect those FairPlay Streaming credential assets at all times, when they are deployed in your server, and when they're used in your server.

Make sure they are protected.

So now moving on to the diagram, we've got the server components on the left-hand side, namely your key server that has the FairPlay Streaming key security module integrated in it; the key database that contains the content key values that were used to encrypt your streams. And then on the right-hand side we've got the client actors, namely your application, the AVFoundation Delegate Roger was talking about, and AVFoundation that's provided us part of the operating system with our iOS or Mac OS X. So lLet's talk about what happens when the user hits play in your application. First thing that's going to happen is, your application is going to invoke AVFoundation and provide it with the m3u8 URL to the encrypted content. AVFoundation is going to pull that playlist from the Internet, it's going to parse it, and when it notices that the content is encrypted, it is going to call back into your delegate, telling it that it needs a key to play the content. The delegate is going to handle that by calling into AVFoundation and asking it to create what we refer to as the Server Playback Context.

In FPS parlance we use SPC for short. And what that is, is a key request that your delegate then is going to post to your key server in order for the key server to do its job and deliver the content key. What is important to note here is that the SPC is created in a FairPlay Streaming delivery context on the client. And that is a session-specific context that only that device was able to create, for which that device will only be able to process the response from the server. It is tied to the device and to that session.

So then your server is going to make use of the KSM to crack that SPC queue request open, validate it from a format point of view and from a cryptographic point of view, and look up the corresponding content key in the key server database.

It's going to then wrap that content key value into what we refer to as a content key context, or CKC for short, and the last step that your app delegate is going to perform, is provide that CKC back to AVFoundation.

So, at this point the device has everything it needs to decrypt and play the content.

So now that we've covered the actors and the data flows in a FairPlay Streaming system, let's talk about what Apple provides.

We provide AVFoundation, of course. And part of AVFoundation in iOS and Mac OS is the API that you are going to be using to implement the delegate.

Another thing we provide is the FairPlay Streaming SDK on developer.apple.com. And that SDK contains a certain number of things. First of all, it contains a protocol specification that has all the details on how the SPC and the CKC messages are formatted, and which cryptographic primitives you are going to use to process the incoming key requests and also generate the key response.

It contains a key security module server reference implementation in NCC.

It contains a full suite of server test vectors and validation tools that you can use for your server development.

It contains some client-side example content.

And the last bit it contains is a set of client example code.

So the responsibilities of your key server are going to be, as Roger pointed out, first of all, the decryption and the validation of the SPC key request. Then it is going to look up the content key based on the asset identifier that the customer wants to play, and then it is going to produce the CKC response. It's the first and third operation that are going to be taking place in your KSM. And the way you go about implementing that is two fold. You can either decide to implement the logic from scratch using the protocol specification that's provided in the FPS SDK.

Or you can just take the C reference implementation and customize it either by using your language of choice or by integrating it directly into your existing key server. So now that that's integrated, let's talk about how you are going to test the KSM.

Well, the first thing we recommend you do is obviously use the supplied test vectors that are part of the SDK to validate the correctness of the responses that your KSM is going to produce. And the way you go about doing that is using the supplied SPC test vectors, feed them to your KSM implementation, and then run the output CKC that your KSM produced through the validation tool to make sure they are correct both from a cryptographic point of view and from a format point of view.

It is important to note that the test vectors we provide in the SDK are based on development credentials. And they are there exclusively for your development effort. They cannot be used to deploy a solution to live customer devices. To do that you're going to need production FairPlay Streaming credentials. So now that we've talked about the server side, let's talk about the client side. What does it take to integrate FairPlay Streaming into your application? Well, the first thing you're going to want to do is register an AV asset resource loader delegate with AVAsset, and the responsibilities of that delegate are three fold. The first thing it's going to be doing is generating the SPC. And you do that by implementing these two steps. You're first going to handle 'should wait for loading of requested resource' for the key requests.

And then second of all you're going to call 'AVAsset resource loading request streaming content key request data for app' to produce the SPC. Once you've got that SPC in hand, you're going to send it to your key server. And when your key server responds, you're going to provide the CKC response to 'AVAsset resource loading request.' So we've got the server side implemented; we've got the client side implemented. Let's talk about the workflow updates in your content authoring.

What are you going to have to do to encrypt the content? Well, the first thing you should do is go pull the HLS Sample Encryption specifications from developer.apple.com, and that will provide you with all the details you need to know about encrypting the bit stream itself, whether audio or video. Once you have got that bit stream encrypted you're going to have to update the m3u8 playlist to signal, first of all, what type of encryption mode you use. And that, you do that by setting the method tag in the m3u8 playlist to Sample-AES.

Another signal you want to send to the client is the fact that you want to use FairPlay Streaming for the key delivery. And the way you do that is an update to another tag in the m3u8 playlist, that's the key format tag, you want it to set it to com.apple.streamingkeydelivery.

The fact that we've deployed it for over three years now means that there's quite some third-party support in the encoders out there right now. And you can choose to go with one of those as an alternative to making updates to the workflow yourself.

Once you have got your workflow updated, here is how you go about checking the correctness of that encryption workflow.

You can do basically two comparisons. But they both start in the same way. You start by taking a clear text piece of content from the sample SDK and run that through your new workflow. And then you can compare it either to the same encrypted asset in the SDK, or you can compare it to an encrypted version of that asset that you run through the HLS media file segmenter. The reason why the second point is interesting is because you can do it with your own content as well rather than the sample content.

So now that we've talked about what it takes to develop the client side and the server side, and updates to your workflow, that leads us to functional local playback. I would like to now talk to you about FairPlay Streaming support in AirPlay. And the support we have for FairPlay Streaming and AirPlay is through the AirPlay video path. And what that means is that when you transition from local playback in your application to the Apple TV, it is actually the Apple TV that is pulling the bits from the Internet, right? It is not the sender device anymore.

And the good news here is that no new additional code needs to be written either in your application or on the server side. The KSM supports processing increment key requests, both whether they are coming from an Apple TV or from an iOS device.

To be clear, the SPC is still generated on the Apple TV and the CKC response that your key server is producing will also be processed on the Apple TV.

However, your app is still responsible for relaying the messages between the Apple TV and the key server. So the sending device has to be present.

This gives us the same level of security as local playback because the SPC and CKC messages both originate and end on the device that is actually playing the content, the Apple TV, in this case, in the AirPlay case.

One important point to note is the fact that FairPlay Streaming content will not be rendered in AirPlay Mirroring mode. That also applies to screen shots and recordings for FairPlay Streaming content that's played on your local device.

So now that we've spoken about how to consume the content locally on your app or through AirPlay, I'm proud to announce this year that we are adding FairPlay Streaming support to El Capitan.

And the way we go about, the way you would go about integrating this into your website is through the encrypted media extensions that are part of HTML5, that's a W3C specification that you can download on their website.

The way you go about integrating with EME is by writing your key delivery code in JavaScript on your website, and we provide an example of such an implementation in the SDK. It is more of a snippet.

The good news here is that both on the KSM side and on the AirPlay side there is no new code that is needed. It will work out of the box and everything is fully supported once you have got your JavaScript written. So now let's talk about the JavaScript you are going to be writing to add support for FairPlay Streaming in your Webpage. The first thing you're going to do is set the m3u8 URL as a source attribute of the HTML5 video tag as you would for a non-encrypted piece of content.

Then you are going to add an event listener for the Web kit need key call to the video element.

That event listener when triggered is going to set the EME content decryption module to FairPlay Streaming. It is also going to create a key session on video/MP4 to relay the messages between the key system and your key server.

And you're going to add an event handler for web kit key message to that key session. That event handler is going to be the one that's responsible for sending the SPC key request to your key server and then processing the CKC response by updating the key session.

In terms of the data flow, we've got very similar actors on the left-hand side. We have the same ones on the right-hand side. We have got Safari now that Apple provides, along with the EME stack. Within Safari we have got your site, and the new piece of JavaScript code that you are going to be writing to support FairPlay Streaming content playback in your website.

Let's talk about what happens when the user hits play in Safari. So, the user hits play. The first thing that is going to happen is, obviously, the m3u8 is going to hit the EME and AVFoundation in the operating system, and EME is going to notice that the content is encrypted, which is going to cause it to trigger the Web kit need key message that your event listener is going to receive.

Then your event listener is going to create the key session and is going to wait for the Web kit key message, which in turn is going to trigger the handler, and that handler is going to receive the SPC, send it over to your key server, which is going to process it as usual, pull the content key and then create the content key response, send that CKC back to your JavaScript, which will provide it back down to the EME layer for playback.

As Roger described, we've had this solution deployed now for over three years, and over the years we've learned a few tips and tricks on how to troubleshoot integrating issues with FairPlay Streaming. And the typical issue you may be facing, if unfortunately something goes wrong with your integration, is that content doesn't play.

So how do you go about debugging that situation? Well, one thing we recommend you do is -- and this is for debug purposes only, we don't recommend that you do this in a production environment, but -- set your key format tag in the m3u8 playlist to identity, instead of com.apple.streamingkeydelivery. What this does is, it allows the same content to get to your client, but instead of decrypting it with FairPlay Streaming, it decrypts it with a clear text AES key.

And what we end up is either in one of two situations. Your content is still not playing, in which case this is probably facing a content authoring issue, and those issues typically fall into one of four buckets.

Either your sample of encryption has an issue and in that case I'd refer you to the HLS Sample encryption specification. It could be an issue with your PAT/PMT audio set up. Those are steps that you need to perform on audio streams that are encoded, that are encrypted with FairPlay Streaming. There are a few metadata updates that need to happen.

It may be the case that you are not using one of the supported codecs. And as Roger mentioned earlier, what we support right now in FairPlay Streaming is H.264, AAC, and encrypted AC3.

Last but not least, it may be you are rotating your content key on something that isn't an HLS segment. So we recommend that you rotate your keys either on HLS segments at the most granular level or you can also decide to change your content key value on a bit rate switch.

If your content is playing after you update the key format tag to identity, you are probably facing a key delivery issue. And in that case, what you want to do is you want to trace through the data flow that we went through in the earlier diagrams, and make sure that the SPC is properly generated by the client, that it's sent to your server, that your server can process that key request without any failures, that your server is looking up the right key in the database, that your server is also capable of packaging the content key into content key response, and that the client is able to process that without any errors.

So, now that we went over all the various ways of consuming FairPlay Streaming content in the Apple ecosystem, I would like to hand it back to Roger to wrap the session up. Thank you very much for your time. ROGER PANTOS: Thanks very much, GP. So, let's do a quick recap here.

FairPlay Streaming for HTTP Live Streaming, it provides you with industrial strength tools to protect your content with HTTP live streaming. You have got it available on iOS, on Apple TV, and now on OS X. iOS, it's available since iOS 6, so there's a fair amount of backward compatibility, and also on Apple TV. OS X is a little bit newer, and so you can come down and talk to us in the labs, and we will give you the entire scoop on where you can use it. It has been deeply integrated into the OS. That means that it is down as low as we can get it, as secure as we can make it. It is as power efficient as we can do. And so it gives you great battery life as well as great security.

And it also supports all of our ecosystem features such as AirPlay, such as HDCP, HTML5, and we will continue to do so as we roll out new features going forward.

So, what's next? First stop is our new FairPlay Streaming portal on developer.apple.com. It's live now, so you can go there, you know, you can go there right now. And you can, from there you can download the SDK. You can look at the overview document that gives you a little bit of a deeper insight into some of the details of FairPlay Streaming. And you can also, through that site, apply for your production developer credentials that are necessary for you to do your round trip playback to an actual iOS device or Safari.

And the next thing, and I should also mention, actually, that on that site, on that landing page there, there may be some of you who don't have an existing back end or are a little bit intimidated by the idea of integrating FairPlay Streaming into that back end. So on that landing page we have a little list of integration partners we've worked with, folks like Irdeto, folks like Adobe, who have set up some support for folks who wish to use FairPlay Streaming to protect their HLS content. And so I would recommend checking out those folks as well. If you feel like you need a little bit of help getting FairPlay Streaming up and running for your content.

It is, it's, I think it's pretty easy to do, but not everyone is in that business. And so there's help for you there if you need it.

Also, if you would like to get HLS and FPS working, and it feels a little bit like there're still questions or you've tried it and you've got some problems, if you are not at WWDC, then your best first stop is our developer forums. And we've actually set up, I believe it's in the beta section right now, but we've set up a new forum specifically for FairPlay Streaming. And so check that out. If you are running into a problem or you have got a question, there's pretty good odds that somebody else has had the same question, same problem, and you might just be able to find the answer by looking in the forums. Failing that, there is, of course, your friendly neighborhood developer tech support representative who will be happy to assist you for a small fee.

I think that's it.

Thank you again for coming. And have a great show! [Applause]