MP4Box and clear key encryption?

[Don Metzler]

Does MP4Box support clear key encryption?

[Jean Le Feuvre]

MP4Box supports Common Encryption using either CBC or CTR modes, and supports protecting a file with multiple systems.
Could you please explain what clear key encryption consists of ?

[ljl]

Hi,

I try to crypt a mp4 video with MP4Box that i have installed on linux, using clear key format as described here: https://html5.cablelabs.com/mse-eme/doc/creation.html,
to be able to manage EME/MSE .

For that, i pass a drm file to MP4Box that has value described in the upper page :

<GPACDRM type="CENC AES-CTR"> <DRMInfo type="pssh" version="0"> <BS ID128="9a04f07998404286ab92e65be0885f95"/> <BS bits="32" endian="little" value="762"/> <BS bits="16" endian="little" value="1"/> <BS bits="16" endian="little" value="1"/> <BS bits="16" endian="little" value="752"/> <BS data64="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"/> </DRMInfo> <CrypTrack IV_size="8" first_IV="0x81171442af182143" isEncrypted="1" saiSavedBox="senc" trackID="1"> <key KID="0x10000000100010001000100000000001" value="0x3a2a1b68dd2bd9b2eeb25e84c4776668"/> </CrypTrack> </GPACDRM>

MP4Box -crypt drm_file.xml movie.mp4 -out movie_encrypted.mp4

What i can see (using verbose) is that crypting does not occur .

As a consequence the video is never crypted (i can play it with VLC player).

Now, if i use ISMA syntax, i can crypt the video.

<ISMACryp> <ISMACrypTrack trackID="2" key="0x2b7e151628aed2a6abf7158809cf4f3c" salt="0xf8f9fafbfcfdfeff" scheme_URI="http://schemas.microsoft.com/DRM/2007/03/PlayReadyHeader" kms_URI="http://playready.directtaps.net/pr/svc/rightsmanager.asmx?PlayRight=1&amp;UseSimpleNonPersistentLicense=1" selectiveType="None" ipmpType="None"/> </ISMACryp>

But i am not able to decrypt is using EME/MSE , for instance using a html file like this :
http://simpl.info/eme/clearkey/

So my questions are :
- What xml file should i have to use clear key encryption
- When i tape : MP4Box -h crypt : it only gives information on ISMACryp
does it mean there was some arguments to pass at the compilation time to be able to manage clear key ?
- I tried also to manage webm format , but it seems even ISMA crypt does not work

thanks for the feed backs

Regards

[Viet-Thanh-Trung NGUYEN]

Hi,
I think that you have a problem with trackID in drm file. In case of ISMA (which it worked) your trackID is 2, while in the first case you used trackID=1. Try to change it to trackID=2 !

[ljl]

Hi,

no it is not a track Id problem.
I have also the problem with :

<GPACDRM type="CENC AES-CTR"> <DRMInfo type="pssh" version="1" cypherOffset="9"> <BS ID128="6770616363656E6364726D746F6F6C31"/> <BS value="2" bits="32"/> <BS ID128="0x279926496a7f5d25da69f2b3b2799a7f"/> <BS ID128="0x676cb88f302d10227992649885984045"/> <BS bits="8" string="CID=Toto"/> <BS ID128="0xccc0f2b3b279926496a7f5d25da692f6"/> <BS ID128="0xccc0f2b3b279926496a7f5d25da692d6"/> </DRMInfo> <CrypTrack trackID="2" IsEncrypted="1" IV_size="16" first_IV="0x0a610676cb88f302d10ac8bc66e039ed" saiSavedBox="senc"> <key KID="0x279926496a7f5d25da69f2b3b2799a7f" value="0xccc0f2b3b279926496a7f5d25da692f6"/> </CrypTrack> </GPACDRM>

now looking at the video :
MP4Box -info video.mp4 , the video is not encrypted.

Does MP4Box allow to manage clear key encoding (needed for EME/MSE) ?
if yes, how ?

thanks
Regards

[Viet-Thanh-Trung NGUYEN]

It is not normal that encrypting doesn't work. Could you please post your video somewhere, we will verify that !
MP4Box supports Common Encryption using either CBC or CTR modes; you can check http://gpac.wp.mines-telecom.fr/mp4box/encryption/common-encryption/ for more information.

[ljl]

Hi,

i have posted the video

Regards

[Viet-Thanh-Trung NGUYEN]

Hi,

I've tried to encrypt your video using the lastest GPAC version (rev 497, found here: http://gpac.wp.mines-telecom.fr/downloads/gpac-nightly-builds/#Windows%2064%20bits) with drm file as you used, and the video track (trackID = 2) was encrypted (see in attachment). when I played file encrypted.mp4, there was only audio (track 1).
Command: MP4Box -crypt drm_file.xml big_buck_bunny.mp4 -out encrypted.mp4
Could you please retry ?

[ljl]

Hi,

Previously i used version 0.4.5 on linux , after have installed binary and gpaclib.so

I get the gpac-0.5.2-DEV-rev497-gf85197f-master-x64.exe, and using cmd console from window, i can see the video is crypted :

MP4Box -crypt drm_file.xml big_buck_bunny.mp4 -out encrypted.mp4

[Viet-Thanh-Trung NGUYEN]

THis is an installer, you install it and open the CommandLine (cmd) for using MP4Box. If you prefer Linux, you can also download the latest version for Linux 32/64 bits: http://gpac.wp.mines-telecom.fr/downloads/gpac-nightly-builds/

[ljl]

Ok, now i try to use Clear key content of microsoft play Ready, using this xml file :

<GPACDRM type="CENC AES-CTR"> <DRMInfo type="pssh" version="0"> <BS ID128="9A04F07998404286AB92E65BE0885F95"/> <BS data="application/data;base64:ACE125"/> <BS sourceFile="cenc_blob.bin"/> </DRMInfo> <DRMInfo type="pssh" version="1" cypherOffset="9" cypherKey="0x6770616363656E6364726D746F6F6C31" cypherIV="0x00000000000000000000000000000001"> <BS ID128="6770616363656E6364726D746F6F6C31"/> <BS value="2" bits="32"/> <BS ID128="0x279926496a7f5d25da69f2b3b2799a7f"/> <BS ID128="0x676cb88f302d10227992649885984045"/> <BS bits="8" string="CID=Toto"/> <BS ID128="0xccc0f2b3b279926496a7f5d25da692f6"/> <BS ID128="0xccc0f2b3b279926496a7f5d25da692d6"/> </DRMInfo> <CrypTrack trackID="2" IsEncrypted="1" IV_size="16" first_IV="0x0a610676cb88f302d10ac8bc66e039ed" saiSavedBox="senc"> <key KID="0x279926496a7f5d25da69f2b3b2799a7f" value="0xccc0f2b3b279926496a7f5d25da692f6"/> </CrypTrack> </GPACDRM>

Video is correctly encrypted using : MP4Box -crypt drm_file.xml big_buck_bunny.mp4 -out encrypted.mp4

Then, i try to use EME/MSE html script to check if encrypted video can be decoded :

I use the key 0x279926496a7f5d25da69f2b3b2799a7f in the javascript, but the video is still crypted.

I can see following error in Chrome PC inspector :

main_mp4.js:38 Failed to set up MediaKeys DOMException: None of the requested configurations were supported.

Do you know if the key i have used is correct ?
and if MP4Box manages this type of encryption ?

thanks

Regards

[Viet-Thanh-Trung NGUYEN]

Hello,

I don't know how the script works, so I can't tell you whether it's correct or not. Please contact an expert of EME/MSE for more information.
FYI, when I play the encrypted video using our playback (MP4Client) it works well;

[ljl]

Hi,

I managed following sequence :

MP4Box -v -crypt drm_file_play_ready.xml big_buck_bunny.mp4 -out encoded_big_buck_bunny.mp4

I attach different files for information.

Using playreadyKeyGen.java, i got the correspondence between UUID key and needed elements for xml files:

===============================================
Content key ID =
0x20000000200020002000200000000002
0x00000020002000202000200000000002 (MS binary)
IAAAACAAIAAgACAAAAAAAg== (Base64)
AAAAIAAgACAgACAAAAAAAg== (Base64, MS binary)
Content key =
0x881494BC53A489479F267A521C9FE343
iBSUvFOkiUefJnpSHJ/jQw== (Base64)
Checksum =
0x7E6FB722F7601675
fm+3IvdgFnU= (Base64)
IV =
0x6403E7BBEBA1B785
ZAPnu+uht4U= (Base64)
===============================================
I can check the video encoded_big_buck_bunny.mp4 is crypted.

Now, the problem i have, is to decrypt it using javascript .
I tries several approaches :
- Put the key Id in hex in javascript , like it is done in http://simpl.info/eme/clearkey/

• Use dash.js with a manifest file that has a syntax using

<ContentProtection schemeIdUri="urn:mpeg:dash:mp4protection:2011" value="cenc" cenc:default_KID="20000000-2000-2000-2000-200000000002"/>

• Use MP4Client to read video encoded_big_buck_bunny.mp4

None of them can decrypt the video.

So my question is :
How to check the video is correctly encrypted with clear key ?

PS:

I use following syntax to play encrypted video using MP4Client

MP4Client -show -opt section:key=0x20000000200020002000200000000002 encoded_big_buck_bunny.mp4

Is it the correct syntax ?

I have errors :

[h264 @ 000000000051acc0] illegal reordering_of_pic_nums_idc
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] deblocking_filter_idc 27 out of range
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] top block unavailable for requested intra mode at 3 0
[h264 @ 000000000051acc0] error while decoding MB 3 0
[h264 @ 000000000051acc0] slice type 32 too large at 3 0
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] non-existing PPS 2 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] no frame!
[h264 @ 000000000051acc0] SEI type 181 size 952 truncated at 142
[h264 @ 000000000051acc0] non-existing PPS 1 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] non-existing PPS 3 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] slice type 32 too large at 3 0
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] non-existing PPS 29 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] non-existing PPS 1 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] no frame!
[h264 @ 000000000051acc0] SEI type 64 size 1832 truncated at 143
[h264 @ 000000000051acc0] top block unavailable for requested intra4x4 mode -1 at 11 0
[h264 @ 000000000051acc0] error while decoding MB 11 0
[h264 @ 000000000051acc0] deblocking filter parameters 98 44 out of range
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] non-existing PPS 19 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] non-existing PPS 2 referenced
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] slice type 10 too large at 2 0
[h264 @ 000000000051acc0] decode_slice_header error
[h264 @ 000000000051acc0] no frame!
[h264 @ 000000000051acc0] SEI type 46 size 376 truncated at 143
[h264 @ 000000000051acc0] left block unavailable for requested intra mode at 0 0

Concerning the KID, KeyValue needed to decrypt the video,
have you already tested a MP4 video crypted with Mp4Box using clear key encoding can be decrypted using javascript (by giving the key ) ?

The problem i have is :
If we look at http://simpl.info/eme/clearkey:

• It uses a clear key for a webm video that can be played using javascript with the key passed, which is correct.

• If i change the last byte of the key, the video is no more played, and there is an "error event" in inspector, which seems correct.

• Now, if i play the video crypted by MP4Box, i have an other error which is "DOM exception: Failed to set media keys"

So my question is :
Has someone already used MP4Box to crypt and decrypt MP4 video using clear key encryption, and has decrypted it using javascript ?

Thanks

Regards

[Viet-Thanh-Trung NGUYEN]

Hello,
You can't play the crypted video using MP4Client because you use playready as the DRM server, you need a playback which support retrieving the info from playready server (like KID, key value ...) and use it to decrypt file.