How to generate decryption key from m3u8 manifest? (OR) How to decrypt an excrypted MP4 using URI and IV?

Question

I am downloading an HLS video which is AES-128 encrypted. The issue is that the downloaded video is also encrypted and hence, not viewable.

The website is serving 2 M3U8 manifests:

1. The first manifest (playlist.m3u8) refers to a chunklist_alphanumeric.m3u8. A sample is here.

2. The second manifest (chunklist_alphanumeric.m3u8) seems like this.

In this context, I have the following two questions

1. How can I generate the decryption key?

2. How can I decrypt the video using the decryption key?

I'm using Windows-10 (64-bit).

Answer 1

You cant generate the key. You have to download the key. The URL is in the manifest. In this case it looks like you need to substitute some values first.

To decrypt, since this files uses AES-128 and not SAMPLE-AES, you can just decrypt each file using OpenSSL