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Android cast playing a video with custom encryption

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1

1

I have an android app that plays some video content. The video is mp4 with some simple custom encryption.
In android the player (ExoPlayer) decrypts the video in real time while playing.

It uses a code like this:

// overriding the function that reads the video file to insert the decryption
public int read(byte[] buffer, int offset, int readLength) throws FileDataSourceException 
 // ...
 // buffer[] holds the video bits, decrypt them here
 buffer[offset] = (byte)(buffer[offset] ^ 1234);

 // ...
 
}

I now want to add support for Chrome cast - to be able to stream the video from a mobile phone to tv.

However looking at the api I cannot see a way to implement my decryption algorithm.
From what I see it supports either unencrypted videos or videos with some standard DRM.

Is it possible to implement a custom encryption, similar to the code above?

android chromecast drm

share|improve this question

edited Mar 22 at 9:30

Lacho Tomov

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  If your looking for DRM of Chromecast support, there is an available blogpost about the support of DRM encryption on the ChocoTv. This will let Chromecast support HLS AES-128 encryption for Android Platform. Check this site for more details.
  
  – jess
  Mar 22 at 9:23
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @jess thanks, I'll take a look. I was hoping to avoid using the standard encryption/drm algorithms and go with something simple as shown in the code above (i just added it). But it looks like I may need to go this way.
  
  – Lacho Tomov
  Mar 22 at 9:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  If you're looking for actual security, unless you have a PHD in math, give up on the idea of writing anything yourself. The difficulty in writing an effective encryption mechanism is immense.
  
  – Gabe Sechan
  Mar 23 at 0:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @GabeSechan actually implementing something simple like XOR encryption is quite easy and it will guard against 99% of the attackers. The remaining 1% will break it, but they will break your DRM encryption as well, so in many cases it's not worth the time and effort.
  
  – Lacho Tomov
  Mar 23 at 15:12
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  No, it isn't. While a otp is unbreakable if not reused, you will be reusing it constantly, and you aren't even thinking about key exchange. You aren't actually giving it any real security, just the veneer of it. And if you think anyone is breaking aes outside the NSA, you're insane. Just use an existing algorithm and a library for it (to minimize your chance of worrying a side channel attack)
  
  – Gabe Sechan
  Mar 23 at 16:07
  
  

  
  
  
  

 | 
show 3 more comments

1

1

I have an android app that plays some video content. The video is mp4 with some simple custom encryption.
In android the player (ExoPlayer) decrypts the video in real time while playing.

It uses a code like this:

// overriding the function that reads the video file to insert the decryption
public int read(byte[] buffer, int offset, int readLength) throws FileDataSourceException 
 // ...
 // buffer[] holds the video bits, decrypt them here
 buffer[offset] = (byte)(buffer[offset] ^ 1234);

 // ...
 
}

I now want to add support for Chrome cast - to be able to stream the video from a mobile phone to tv.

However looking at the api I cannot see a way to implement my decryption algorithm.
From what I see it supports either unencrypted videos or videos with some standard DRM.

Is it possible to implement a custom encryption, similar to the code above?

android chromecast drm

share|improve this question

edited Mar 22 at 9:30

Lacho Tomov

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  If your looking for DRM of Chromecast support, there is an available blogpost about the support of DRM encryption on the ChocoTv. This will let Chromecast support HLS AES-128 encryption for Android Platform. Check this site for more details.
  
  – jess
  Mar 22 at 9:23
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @jess thanks, I'll take a look. I was hoping to avoid using the standard encryption/drm algorithms and go with something simple as shown in the code above (i just added it). But it looks like I may need to go this way.
  
  – Lacho Tomov
  Mar 22 at 9:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  If you're looking for actual security, unless you have a PHD in math, give up on the idea of writing anything yourself. The difficulty in writing an effective encryption mechanism is immense.
  
  – Gabe Sechan
  Mar 23 at 0:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @GabeSechan actually implementing something simple like XOR encryption is quite easy and it will guard against 99% of the attackers. The remaining 1% will break it, but they will break your DRM encryption as well, so in many cases it's not worth the time and effort.
  
  – Lacho Tomov
  Mar 23 at 15:12
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  No, it isn't. While a otp is unbreakable if not reused, you will be reusing it constantly, and you aren't even thinking about key exchange. You aren't actually giving it any real security, just the veneer of it. And if you think anyone is breaking aes outside the NSA, you're insane. Just use an existing algorithm and a library for it (to minimize your chance of worrying a side channel attack)
  
  – Gabe Sechan
  Mar 23 at 16:07
  
  

  
  
  
  

 | 
show 3 more comments

I have an android app that plays some video content. The video is mp4 with some simple custom encryption.
In android the player (ExoPlayer) decrypts the video in real time while playing.

It uses a code like this:

// overriding the function that reads the video file to insert the decryption
public int read(byte[] buffer, int offset, int readLength) throws FileDataSourceException 
 // ...
 // buffer[] holds the video bits, decrypt them here
 buffer[offset] = (byte)(buffer[offset] ^ 1234);

 // ...
 
}

I now want to add support for Chrome cast - to be able to stream the video from a mobile phone to tv.

However looking at the api I cannot see a way to implement my decryption algorithm.
From what I see it supports either unencrypted videos or videos with some standard DRM.

Is it possible to implement a custom encryption, similar to the code above?

android chromecast drm

share|improve this question

edited Mar 22 at 9:30

Lacho Tomov

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

// overriding the function that reads the video file to insert the decryption
public int read(byte[] buffer, int offset, int readLength) throws FileDataSourceException 
 // ...
 // buffer[] holds the video bits, decrypt them here
 buffer[offset] = (byte)(buffer[offset] ^ 1234);

 // ...
 
}

android chromecast drm

android chromecast drm

share|improve this question

edited Mar 22 at 9:30

Lacho Tomov

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

share|improve this question

edited Mar 22 at 9:30

Lacho Tomov

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

asked Mar 21 at 8:01

Lacho TomovLacho Tomov

1,2261524

1 Answer
1

active

oldest

votes

1

The new CAF framework provides three different options:

• Styled Media Receiver


• Custom Receiver


• Default Media Receiver

The only one which supports DRM is the custom receiver and as you say it is designed for the standard DRM's.

However it should support CENC clear key which may be enough protection for your needs and will allow you avoid using a DRM service.

CENC clear key has the key in the clear as the name suggests. It is not very secure but it may be enough of a 'hurdle' (which is essentially what most security systems are) for you anyway.

share|improve this answer

edited Mar 25 at 10:42

answered Mar 22 at 10:58

MickMick

12.7k12464

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  CENC sounds like a good option, I'll investigate it deeper. Thanks!
  
  – Lacho Tomov
  Mar 22 at 11:34
  

  
  
  
  

add a comment | 

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1

The new CAF framework provides three different options:

• Styled Media Receiver


• Custom Receiver


• Default Media Receiver

The only one which supports DRM is the custom receiver and as you say it is designed for the standard DRM's.

However it should support CENC clear key which may be enough protection for your needs and will allow you avoid using a DRM service.

CENC clear key has the key in the clear as the name suggests. It is not very secure but it may be enough of a 'hurdle' (which is essentially what most security systems are) for you anyway.

share|improve this answer

edited Mar 25 at 10:42

answered Mar 22 at 10:58

MickMick

12.7k12464

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  CENC sounds like a good option, I'll investigate it deeper. Thanks!
  
  – Lacho Tomov
  Mar 22 at 11:34
  

  
  
  
  

add a comment | 

1

The new CAF framework provides three different options:

• Styled Media Receiver


• Custom Receiver


• Default Media Receiver

The only one which supports DRM is the custom receiver and as you say it is designed for the standard DRM's.

However it should support CENC clear key which may be enough protection for your needs and will allow you avoid using a DRM service.

CENC clear key has the key in the clear as the name suggests. It is not very secure but it may be enough of a 'hurdle' (which is essentially what most security systems are) for you anyway.

share|improve this answer

edited Mar 25 at 10:42

answered Mar 22 at 10:58

MickMick

12.7k12464

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  CENC sounds like a good option, I'll investigate it deeper. Thanks!
  
  – Lacho Tomov
  Mar 22 at 11:34
  

  
  
  
  

add a comment | 

The new CAF framework provides three different options:

• Styled Media Receiver


• Custom Receiver


• Default Media Receiver

The only one which supports DRM is the custom receiver and as you say it is designed for the standard DRM's.

However it should support CENC clear key which may be enough protection for your needs and will allow you avoid using a DRM service.

CENC clear key has the key in the clear as the name suggests. It is not very secure but it may be enough of a 'hurdle' (which is essentially what most security systems are) for you anyway.

share|improve this answer

edited Mar 25 at 10:42

answered Mar 22 at 10:58

MickMick

12.7k12464

share|improve this answer

edited Mar 25 at 10:42

answered Mar 22 at 10:58

MickMick

12.7k12464

answered Mar 22 at 10:58

MickMick

12.7k12464

answered Mar 22 at 10:58

MickMick

12.7k12464