What does that mean ?

[georgesgiralt]

Hello Guys,
When I launch my Makemkv version, my drive reports :

Code: Select all

Bus encryption flags: 1F
Highest AACS version:82

I can understand that the AACS line pertains about the latest seen AACS version by the drive.
But what "Bus encryption flag" is and what does the values 1F means ?
Also, when ripping a disc, I've a line like

Code: Select all

Libre drive id : 0x??? 

with the question marks replaced by a series of numbers.
Same question as above, what does that mean and what is the use ?
Thanks a lot in advance for helping me understand more !
Have a nice day !

[AstralWanderer]

See the LibreDrive and Encryption? thread for more details.

[georgesgiralt]

Thank you AstralWanderer for the link. But if this explains the bus encryption technique and use, it does not answer what the "1F" value means.
Also, no info on the Libredrive value.
So my question still stand, even if I now know way more than before.

[Sayaka]

it does not answer what the "1F" value means.

I actually have a theory about that one (to anyone who knows more than me, please feel free to correct me if I'm wrong ).

When I look at the possible values, it looks a lot like Byte Number 4 (which is actually the fifth byte, since you have to take Byte Number 0 into account) of the AACS Feature Descriptor defined in this AACS standard : https://aacsla.com/wp-content/uploads/2 ... l_0953.pdf (see page #52, on my computer the actual page number is 65)

If I am correct, Bit 0 is the Binding Nonce Generation bit, Bit 1 is the Bus Encryption Capable bit, Bit 2 is the Write Bus Encryption bit, Bit 3 is the RMC bit ("Return Media key block for Content protection of recordable media"), and Bit 4 is the Read Drive Certificate bit. Bits 5, 6, and 7 are reserved and should be irrelevant.

So a drive with a "Bus encryption flags" value of 1F would have a binary value of 00011111, which would mean that the drive supports all of these features.

[georgesgiralt]

Yes ! A description and a reference for the sleepless nights !
Have a nice and bright night

[Sayaka]

Have a nice and bright night

Thank you, and it's always nice to have someone notice what my nickname means.

[AstralWanderer]

When I look at the possible values, it looks a lot like Byte Number 4...of the AACS Feature Descriptor defined in this AACS standard : https://aacsla.com/wp-content/uploads/2 ... l_0953.pdf (see page #52, on my computer the actual page number is 65)

Thanks for the info - and double thanks for the hangover that AACS specification document has now given me...

If I am correct, Bit 0 is the Binding Nonce Generation bit...a drive with a "Bus encryption flags" value of 1F would have a binary value of 00011111, which would mean that the drive supports all of these features.

So drives with Bus Encryption flags of 17 (commonly reported here, which translates to 00010111) would only be missing the Return Media Key Block flag.

[Sayaka]

So drives with Bus Encryption flags of 17 (commonly reported here, which translates to 00010111) would only be missing the Return Media Key Block flag.

Assuming I am correct about the whole "AACS Feature Descriptor" hypothesis, that is indeed what it would mean.

Also when the Bus Encryption Flag (BEF) bit of the User Control Data for a Blu-ray *disc* (not drive) is set to 1 (it is the 8th bit so 10000000), this translates to a hex value of 80... which is exactly the value of the Bus encryption flags below "Disc Information" in MakeMKV, when one is dealing with a UHD disc.

Thanks for the info - and double thanks for the hangover that AACS specification document has now given me...

You're welcome. And yes, this document can be a tad headache-inducing.