AES-128 in DASH MPD file

[raknitir]

Good afternoon, it's been some days that I tried to decrypt a video that uses a MPD+AES 128 CBC key, I tried seeking the tutorial:
https://forum.videohelp.com/threads/413718-My-journey-with-AES-128-encrypted-HLS
https://forum.videohelp.com/threads/414202-%5BSOLVED%5D-AES-128-encryption-using-a-DAS...-manifest-file
I checked also other topics, but I didn't find anything regarding MPD + AES 128 that resembles the problem I have.
Sorry to the staff if it was asked before(it seems not)

I checked the requests(all of them) but I didn't find any possible "key". What to do in such cases? I tried to access the link:
keyUriTemplate
But nothing, it fails asking for a parameter.
I was able to find the IV and also the code that "decrypts" the frames in javascript, but it's a mess.
Any suggestion to what to do in such cases?
What makes me wonder is that there is no request to the "CryptoPeriod keyUriTemplate=" found in the mpd, still the webpage can decrypt the frames.

Before I was able to use yt-dlp and it was enough to download it(simple MPD no encryption), but now it's impossible.

For stream(by microsoft) they were using M3U8 + AES 128 CBC if I'm not wrong and I could get the keys by the requests, while on sharepoint I can't find it.
If someone can point me to some guides/tutorials it would help me a lot.

[slayer36]

Good afternoon, it's been some days that I tried to decrypt a video that uses a MPD+AES 128 CBC key, I tried seeking the tutorial:
https://forum.videohelp.com/threads/413718-My-journey-with-AES-128-encrypted-HLS
https://forum.videohelp.com/threads/414202-%5BSOLVED%5D-AES-128-encryption-using-a-DAS...-manifest-file
I checked also other topics, but I didn't find anything regarding MPD + AES 128 that resembles the problem I have.
Sorry to the staff if it was asked before(it seems not)

I checked the requests(all of them) but I didn't find any possible "key". What to do in such cases? I tried to access the link:
keyUriTemplate
But nothing, it fails asking for a parameter.
I was able to find the IV and also the code that "decrypts" the frames in javascript, but it's a mess.
Any suggestion to what to do in such cases?
What makes me wonder is that there is no request to the "CryptoPeriod keyUriTemplate=" found in the mpd, still the webpage can decrypt the frames.

Before I was able to use yt-dlp and it was enough to download it(simple MPD no encryption), but now it's impossible.

For stream(by microsoft) they were using M3U8 + AES 128 CBC if I'm not wrong and I could get the keys by the requests, while on sharepoint I can't find it.
If someone can point me to some guides/tutorials it would help me a lot.

share video url

[larley]

Yes please i've been looking for a manifest like this

[raknitir]

Sadly I can't it's a work account and a work video any idea of where to look? Is it possible that the key is inside the url(so without making a request?)
I'm continuing searching a solution.

[larley]

The key and IV are inside the manifest.
Could you send me a PM regrading the manifest? I really need it to develop my downloader.

[lomero]

@larley

have you tried the search filed on the forum? there are many posts about aes-128

https://www.videohelp.com/search?siteurl=forum.videohelp.com&q=aes-128

[larley]

Yes, for HLS, but not DASH. There's only one thread about this but the site metioned removed the Manifests and is now serving raw video files.

[raknitir]

I may have found the key any idea of how to decrypt the file? I tried N_m3u8DL-RE but it doesn't decrypt it even if I provide the supposed key(the files downloaded are the same as the ones I downloaded before encrypted) and IV.

[larley]

Send me the Manifest, i beg you..
Anyways, use this:
https://forum.videohelp.com/threads/414202-[SOLVED]-AES-128-encryption-using-a-DASH-MPD-manifest-file#post2731733

[raknitir]

1) I downloaded the key by using the URI in the KeyURITemplate found in the MPD manifest and I replaced the & with &.
2) I downloaded all the segments using the youtube-dlp with the --keep-fragments argument
3) I modified and used the script found thanks to the solution suggested by larley. That generated two m3u8s and the main one
4) Then I used N_m3u8DL-RE with the main.m3u8 and the key I found previously if the key it's in the same folder it's enough the name of it for example "Key"
I tried to download a video I already had downloaded and it seems that the bitrate is half the original for the mp4.
While the audio gives that warning while merging:
Non-monotonic DTS in output stream.... This may result in incorrect timestamps in the output file.

I noticed also that the audio fragments are 2 times the video's ones(for example 1000 video fragments and 2000 audio fragments)
How to make sure to download the best resolution with yt-dlp?(I can't use -F because is DRM) Just to make does it downloads the best?
Thanks to larley for his help.

I hope this really short "guide" can help someone.

[larley]

--allow-u

with either

-f "bv,ba"

or

-F

and

-f <id>+<id>

[raknitir]

Thanks a lot, do you know of any solution to Non-monotonic DTS in output stream.... This may result in incorrect timestamps in the output file. for the audio file?

[larley]

No, but found this:

[Attachment 80446 - Click to enlarge]

[raknitir]

Thanks I'll make some tests to understand why.

[raknitir]

I downloaded the same video 3 times and it seems the last fragment of the video file is different in one download while in the other two downloads has the same hash. I used the following command, did I do something wrong?
yt-dlp "" --allow-unplayable-formats -o "video" -R "infinite" --fragment-retries "infinite" --file-access-retries "infinite" --retry-sleep linear=1::2 --retry-sleep fragment:1 --cookies cookies.txt --limit-rate 40K --concurrent-fragments 4 --keep-fragments
Are there other tools to download fragments without merging?
I'm a noob sorry.

[larley]

The downloader i mentioned here: https://forum.videohelp.com/threads/415144-AES-128-in-DASH-MPD-file#post2741789 with:

--skip-merge

(not sure why you would want to skip merging if it already decrypts them for you)

[raknitir]

Because N_m3u8DL-RE.exe doesn't decrypt it(MPD + AES 128) and I have to download the fragments using yt-dlp, generate the needed .m3u8 and then run N_m3u8DL-RE on the m3u8. Am I missing something? Thanks for the help.

[larley]

Did you use the modified version that i referenced and provided the key?

--custom-hls-key <key>

The modified downloader should error out with 'need the key' or something when needed but not specified.

[raknitir]

Thanks, I didn't notice it(I read the post above it). I'll try it soon.

[raknitir]

It doesn't detect it's AES 128 and doesn't decrypt it.

[raknitir]

I noticed the last fragment(encrypted) changes every time I download the file, is it corrupted? How can I solve it? Please help me.