Determining compatibility between blu-ray player and discs
 

I have an older blu-ray player that still works great with my TV. Only problem is that many new blu-ray discs I buy won't play on it, even though my older blu-ray discs still play fine. If I buy less recent releases, it's hit or miss whether the disc will play or not. The firmware of the player is updated to the latest version released by the manufacturer (Sony).


My assumption is the problem is due to the AACS consortium at some point no longer including the decryption keys for my Sony player in the MKB (Media Key Block) included on the discs. In trying to bring some order to acquiring new blu-ray discs, my questions are these:


1. Is there a way to find out which version of MKB started excluding my blu-ray player/firmware combination?


2. Is there a way to identify the MKB version of a blu-ray title before purchase? after purchase?

Re: Determining compatibility between blu-ray player and discs
 

Have you checked the model and see if there are any recent firmware updates? I’d start there first.

Re: Determining compatibility between blu-ray player and discs
 

If a player is too old (ie. older than 3 or 4 years from the first appearance on the general electronics market) and there are no firmware updates, then you're wasting your time trying to "hack" the old player.

Easier to just buy a new bluray player.

Re: Determining compatibility between blu-ray player and discs
 

Nowadays I wouldn't waste my time trying to disassemble and modifying the firmware binary. Too much effort for too little in return.

That is unless you're an expert in embedded programming and know how to read the assembly code from disassembled binary files.

Re: Determining compatibility between blu-ray player and discs
 

I think buying a new player may be your best and easiest solution.

Re: Determining compatibility between blu-ray player and discs
 

As I mentioned, "the firmware of the player is updated to the latest version released by the manufacturer (Sony)."

Re: Determining compatibility between blu-ray player and discs
 

No one suggested "hacking" anything. It's a standard-issue retail Sony blu-ray player with standard-issue Sony firmware updates.

Seeking only to increase knowledge and understanding on how to identify compatibility between blu-ray player and blu-ray discs, which is most likely rooted in the versioned AACS MKB embedded on discs not including keys of a particular machine. Buying a "different" blu-ray player would not solve the problem at hand, as any other player could be susceptible to being incompatible with a different subset of discs because of the nature of changing AACS MKB.

Re: Determining compatibility between blu-ray player and discs
 

A current $50 Sony player will play anything.

Re: Determining compatibility between blu-ray player and discs
 

Reply was off topic, states only the obvious, and doesn't address original question.

Re: Determining compatibility between blu-ray player and discs
 

There are semi-public lists of mkb which indicate which particular keys have been revoked in which particular versions. The hard part is figuring which key corresponds to which particular player.

Since this is a verboten topic where we're not allowed to talk about the technical details on this particular message board, you will have to google for it.

Re: Determining compatibility between blu-ray player and discs
 

If you're looking for the timeline of mkb changes since 2006, that information is also semi-public on various other message boards which discuss unofficial bluray playback issues and grey market programs which shall not be named.

It is a matter of compiling such information from various postings on these particular message boards. You will have to google for them.

Re: Determining compatibility between blu-ray player and discs
 

If you want to know what the mkb version is for a particular bluray disc you have and don't want to use a grey market program, another option is to read the details of the AACS specification and figuring out which configuration file the mkb version is hardcoded into.

From what I've read of the public aacs documents, this would require reading the particular configuration file with a hex editor. (Or write your own program to interpret what the data is).

(This assumes you have a computer bluray-r drive).

Re: Determining compatibility between blu-ray player and discs
 

So what's the deal here?

Is Sony passively bricking old blu-ray players by not updating their firmware? Sort of like how Microsoft stops updating and patching old versions of Windows?

Re: Determining compatibility between blu-ray player and discs
 

The public spec of the mkb and subset/difference stuff is outlined in a pdf file "Introduction and Common Cryptographic Elements Book Rev 0.953" on the official aacs website. The section of interest starts around page 15.

The file of interest on bluray discs where all this mkb + subset/difference info is stored in, is: MKB_RO.inf


On commercial movie bluray discs, the bytes 0 to 7 (in hexadecimal) of MKB_RO.inf will usually be: 10 00 00 0C 00 04 10 03

Bytes 8 to 11 will be the MKB version number. For example, bytes 8 to 11 (in hexadecimal) will be:

00 00 00 01 = mkb v1
00 00 00 03 = mkb v3
00 00 00 10 = mkb v16
00 00 00 11 = mkb v17
00 00 00 21 = mkb v33
00 00 00 3F = mkb v63
00 00 00 40 = mkb v64

The rest of the MKB_RO.inf has other data tables which cover various elements related to revocation.

Re: Determining compatibility between blu-ray player and discs
 

Would this surprise anyone? From my own experience, I have a SONY Blu-ray player from 2011 and haven't run into any playback issues with newer titles.

This is the concerning part of modern tech. Since everything is software-driven, companies can simply make things obsolete under the guise of technological progress. "Sorry your gadget is no longer supported, buy a new one" is becoming very accepted these days.

A car built in 1929 can still run and drive today. A record pressed in 1929 can still be played on a turntable in 2020. Will a 2019 Tesla car be allowed to last more than 15 years? Maybe? Will it become "unsupported" by the manufacturer much like Windows XP and rendered useless?

Re: Determining compatibility between blu-ray player and discs
 

Deliberately "bricking" electronic devices via updates has already happened: Sonos speakers.

https://www.engadget.com/2019/12/31/...on-falls-flat/

https://tech.slashdot.org/story/19/1...n-recycle-mode
https://www.reddit.com/r/technology/...ricking_older/

Re: Determining compatibility between blu-ray player and discs
 

I suspect if the aacs folks decided to invoke the "nuclear option" and deliberate brick any and all bluray players, it might bring on a class action lawsuit.

If not, then I suspect there might be some hardcore folks who will hack the firmware on computer bluray-r drives to reverse this "nuclear option". (Currently there are only two computer bluray-r drives manufacturers left on the market: LG and Pioneer).

Re: Determining compatibility between blu-ray player and discs
 

This forum may provide better answers:

https://forum.doom9.org/

Re: Determining compatibility between blu-ray player and discs
 

I suspect that they'll eventually just stop making blu-ray players and discs before that happens. Just abandon the format.

Re: Determining compatibility between blu-ray player and discs
 

The subset/difference scheme used for key revocation on bluray discs, appears to be patented.

If you have a lot of patience and can read technical documents, this is the patent filing for the Naor-Naor-Lotspiech algorithm.

https://patents.google.com/patent/US7010125

Re: Determining compatibility between blu-ray player and discs
 

The original Naor-Naor-Lotspiech research paper is "Revocation and Tracing Schemes for Stateless Receivers".

It can be found at https://www.iacr.org/archive/crypto2...o2001-toc.html

Re: Determining compatibility between blu-ray player and discs
 

Someone must be studying them - new BDs and UHDs are almost always cracked these days on underground sites before release date. Only rarely does a disc's rip get delayed for long.

Re: Determining compatibility between blu-ray player and discs
 

On an reading of the Naor-Naor-Lotspiech algorithm, it should be obvious that cracking the algorithm itself would be a waste of time. The 128-bit AES encryption algorithm used in a "hash like" manner in the subset/difference tree, is not easily crackable.

From reading the aacs spec and running some of the past leaked/pilfered data keys according to the algorithms in the public spec in the "Introduction and Common Cryptographic Elements Book Rev 0.953" pdf document, I suspect the entire subset/difference tree is a giant pyramid where everything is precomputed a priori according to the aes-g3 algorithm outlined on page 13.

The only way to completely undermine this entire subset/difference tree scheme, would be to find the initial key used at the top of the pyramid which all the subsequent keys lower down in the pyramid are calculated from.

Re: Determining compatibility between blu-ray player and discs
 

That seems like a bit of a leap in logic there, not necessarily supported by the provided facts. What is the nature of the playback failure that you're encountering? Are you getting an error message regarding the encryption keys? What model player do you have? Have you tried contacting Sony support? What titles have you had problems with? Is it consistent? That is, do all older titles play every time? And if I newer title doesn't play, that is also consistent?

Re: Determining compatibility between blu-ray player and discs
 

Doing some more number crunching on this data, I wanted to see whether this subset/difference pyramid had one or more master passwords. This involves understanding what the "uv table" is in the MKB_RO.inf file.

I can say definitively that this subset/difference tree is basically a pyramids within pyramids structure. The u-coordinate states what the initial starting location is in the "superpyramid" which a "master key" (probably randomly chosen) is assigned to a "mini pyramid". The subsequent nodes inside this "mini pyramid" anchored by the initial u-coordinate, are calculated from this initial "master key".

So if a hacker cracks the "master key" of a particular mini-pyramid, all the accs folks have to do is change the initial starting location "u-coordinate" to another spot in the superpyramid and assign a totally different new "master key" for this new minipyramid. (There are over 4 billion possible spots within this superpyramid to start a new mini-pyramid).

Even if the 128-bit AES algorithm is cracked, there is still no easy way to crack the entire superpyramid if all the "master keys" are randomly generated.

Naor-Naor-Lotspiech must have thought very thoroughly about this structure, when they first designed it.