Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-14 Thread Jason Holt


On Wed, 9 May 2007, Ali, Saqib wrote:

What about DRM/ERM that uses TPM? With TPM the content is pretty much
tied to a machine (barring screen captures etc)

Will ERM/DRM be ineffective even with the use of TPM?


ERM/DRM/TPM are such poorly defined and implemented products that people have 
started referring to a DRM fairy who people assume will wave her wand and 
solve whatever problem is at hand.  I used to try to draw out the mentioner's 
claims into a concrete proposal that everyone could objectively examine, but 
the conversation rarely progressed that far.  So now I think that, as with 
other crypto proposals, the onus should now be on the proposer to clearly 
delineate what they're proposing and convince us that it's complete and 
correct, rather than us nodding our heads or lashing out at what we assume it 
means.


So I guess the answer to your question is We'd better assume that DRM+TPM 
will be ineffective until we've subjected a specific implementation of it to 
the same level of scrutiny we apply to other cryptosystems, and since DRM+TPM 
proposals tend to be much more complicated than other cryptosystems like SSL, 
that's going to take a very long time.


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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-14 Thread Anne Lynn Wheeler

Jason Holt wrote:
ERM/DRM/TPM are such poorly defined and implemented products that people 
have started referring to a DRM fairy who people assume will wave her 
wand and solve whatever problem is at hand.  I used to try to draw out 
the mentioner's claims into a concrete proposal that everyone could 
objectively examine, but the conversation rarely progressed that far.  
So now I think that, as with other crypto proposals, the onus should now 
be on the proposer to clearly delineate what they're proposing and 
convince us that it's complete and correct, rather than us nodding our 
heads or lashing out at what we assume it means.


somewhat aside ... there was an effort in the very early days of the PC
to look at (hardware) countermeasures to software (and other) piracy
(I don't remember whether i was involved shortly before or after the 
actual announcement of the PC).


starting with 370, the mainframes had unique processor identifications
and licensed software was configured for the specific processor. this
may have been relatively easy to defeat ... but the numbers and costs
involved somewhat created a barrier. It was sufficient to show that
some (illegal) action had to have been taken in order to successfully
prosecute.

because the costs and numbers involved with the PC were so significantly 
different, individual prosecution was harder to justify ... and so the hardware

countermeasures needed to be much more robust. a problem with the investigation
at the time was that tamper-evident technologies were way too expensive
which contributed to the investigation being shelved.

somewhat in the wake of that ... there were various methods like 
specially encoded floppy disks as countermeasure to piracy (i.e.

the floppy disks were not trivially duplicated by normal means).

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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-14 Thread James A. Donald

Jason Holt wrote:
 So I guess the answer to your question is We'd better
 assume that DRM+TPM will be ineffective until we've
 subjected a specific implementation of it to the same
 level of scrutiny we apply to other cryptosystems, and
 since DRM+TPM proposals tend to be much more
 complicated than other cryptosystems like SSL, that's
 going to take a very long time.

TPM can in principle provide effective DRM - it can also
provide effective super root access to your computer for
FBI and the Motion Picture Association of America - it
can do lots of things.  So far it has not done any of
them.

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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-13 Thread Alexander Klimov
On Fri, 11 May 2007, Jon Callas wrote:
 What about DRM/ERM that uses TPM? With TPM the content is
 pretty much tied to a machine (barring screen captures etc)
 Will ERM/DRM be ineffective even with the use of TPM?

There are two different features of TPM: it can work as an embedded
smartcard (to identify computer), and it can be used to vouch for
integrity of booted software. The first feature does not add
much to DRM, because the attacker has the computer. The second feature
can be bypassed if OS or DRM software has exploitable bugs (or
with relatively simple hardware techniques, but let someone
build a bug-free DRM software first :-) ).

 If someone is so impolite that they'll put the TPM chip under
 a scanning electron microscope, they can probably just read
 the bits off.

Actually there is no need for any TPM intrusive methods to
bypass the second feature mentioned above (the first one does
not need to be bypassed since attacker has the computer). Let us
see how TPM works:

  after reset, CPU sends a sequence of messages that report
  hashes of the booted software;

  TPM changes its internal registers (PCRs -- platform
  configuration registers) as a result;

  CPU sends a key to be encrypted and a description of PCR
  values required to decrypt it;

  TPM returns encrypted blob (it stores PCR requirements inside the
  blob).

Once the blob is saved outside, it can be used to make sure that
only required software can access the key:

  after reset CPU reports hashes of booted software and TPM
  changes PCRs;

  CPU send a blob to be decrypted;

  TPM decrypts it, checks PCR requirements, and return the key
  stored inside.

The crucial assumptions here are that (1) TPM cannot be reset
independently of CPU; (2) CPU's boot ROM cannot be changed (note
that in many cases the ROM used for boot is actually flash);
(3) the bus between CPU and TPM cannot be tampered with.

Now, to decrypt any blob there is no need to have a FIB (focused
ion beam) or a scanning electron microscope, because the only
thing an attacker needs is to break one of the above
assumptions, for example, boot Linux, reset TPM by some hardware
manipulation, write a program to send to TPM the needed set of
PCR change requests, send the blob, get the decrypted key, and
print it out.

Note once again that TPM works exactly as expected, the only
problem is that the assumptions do not hold.

-- 
Regards,
ASK

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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-12 Thread Ali, Saqib

Hi Jon,


Rights management systems work against polite attackers. They are
useless against impolite attackers. Look at the way that
entertainment rights management systems have been attacked.
The rights management system will be secure so long as no one wants
to break them. There is tension between the desire to break it and
the degree to which its users rely on it. At some point, this tension
will snap and it's going to hurt the people who rely on it. A
metaphor involving a rubber band and that smarting is likely apt.


What about DRM/ERM that uses TPM? With TPM the content is pretty much
tied to a machine (barring screen captures etc)

Will ERM/DRM be ineffective even with the use of TPM?

Thanks
Saqib Ali

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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-12 Thread Jon Callas


On May 9, 2007, at 5:01 PM, Ali, Saqib wrote:


Hi Jon,


Rights management systems work against polite attackers. They are
useless against impolite attackers. Look at the way that
entertainment rights management systems have been attacked.
The rights management system will be secure so long as no one wants
to break them. There is tension between the desire to break it and
the degree to which its users rely on it. At some point, this tension
will snap and it's going to hurt the people who rely on it. A
metaphor involving a rubber band and that smarting is likely apt.


What about DRM/ERM that uses TPM? With TPM the content is pretty much
tied to a machine (barring screen captures etc)

Will ERM/DRM be ineffective even with the use of TPM?

Thanks
Saqib Ali


Your comment of barring screen captures etc. is a bit like saying  
that won't a bank be safe from robberies barring someone waving a gun  
in a teller's face, etc. Yeah, sure, but doesn't that kinda miss the  
point? DRM works if the attackers are polite. The less polite they  
are, the less well it works.


DRM systems for media are probably more immune to analog hole  
attacks ERM systems. Imagine that someone ERM protected an email  
showing things that Gonzales couldn't remember when he was testifying  
to Congress, or in some stock scandal, etc. A photo of a screen with  
a cell phone camera would be sufficient. We have not (yet) seen an  
attack where someone got a pre-release of a movie and then pointed a  
camera at a laptop screen, but we will.


If you add in a TPM, it depends entirely on how impolite the  
attackers are, as well as the construction of the TPM. One of the  
recent attacks against AACS involved the attackers unsoldering the  
chip and attacking it directly. That's pretty rude, but it worked.


If someone is so impolite that they'll put the TPM chip under a  
scanning electron microscope, they can probably just read the bits  
off. Very few smart cards can survive that.


Remember, this is all a trade-off between the cost of the device and  
the devotion of the attacker. TPM chips have to be very cheap,  
because the customer is ultimately paying for it. That means its  
defenses can't be very thorough. Furthermore, while the owner of the  
device is the attacker, you can't afford very many defenses. If a  
music player, for example, went DOA because it it was dropped, went  
over/under temperature, and so on, it would be a financial nightmare,  
as you probably have to replace them under warranty. People who hate  
DRM would buy devices, monkeywrench them, and then demand a refund.


ERM systems have the advantage that in general the attackers are more  
polite. More people want to break AACS than rights-controlled analyst  
reports. However, once something really juicy happens, like just  
needing the content registration key for a document that will get a  
politician in jail -- well, plenty of people can hack that. Now, all  
of a sudden, the attackers won't be polite, and that metaphor I made  
about a rubber band snapping will seem modest.


Really, you're much better off with real crypto and personnel policies.

Jon

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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-12 Thread Hagai Bar-El
Hello,

On 08/05/07 20:16, Ali, Saqib wrote:
 I was recently asked why not just deploy a Enterprise Right Management
 solution instead of using various encryption tools to prevent data
 leaks.
 
 Any thoughts?

The encryption tools function according to simple, well understood,
and more-or-less enforceable security models. Their assumptions are well
understood and, most importantly, match the environments they run on.
They solve a simple problem, and solve it effectively.

Rights management solutions have complex security models, and run in
environments that do not always satisfy the assumptions. They aim at
providing complex functionality, but they often (always?) fail to
deliver due to their over-complexity and unrealistic assumptions.

If your security needs can be met by the simple functional model of the
encryption tools, then you will prefer to enjoy the assurance and the
reasonable robustness they provide, which is the most desirable feature
after all.

Hagai.

-- 
Hagai Bar-El - Information Security Analyst
T/F: 972-8-9354152 Web: www.hbarel.com

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Re: Enterprise Right Management vs. Traditional Encryption Tools

2007-05-09 Thread Jon Callas


On May 8, 2007, at 10:16 AM, Ali, Saqib wrote:


I was recently asked why not just deploy a Enterprise Right Management
solution instead of using various encryption tools to prevent data
leaks.

Any thoughts?


What problem are you trying to solve?

If you're dealing with a rights-management problem, such as how do  
you give someone a document that they can read on the screen but not  
print, you aren't going to solve that with a cryptosystem.


However, rights management systems have characteristics that are  
different.


Rights management systems work against polite attackers. They are  
useless against impolite attackers. Look at the way that  
entertainment rights management systems have been attacked.


The rights management system will be secure so long as no one wants  
to break them. There is tension between the desire to break it and  
the degree to which its users rely on it. At some point, this tension  
will snap and it's going to hurt the people who rely on it. A  
metaphor involving a rubber band and that smarting is likely apt.


One way this fails is the good old analog hole. People can still  
take pictures of their screens.


Another way this fails is for people to rely upon rights management  
as a cover for sloppiness, anger, or mendacity. If you think you can  
revoke a message or send Mission Impossible documents, you will.  
Someday, someone on the receiving end will use the analog hole. Oops.  
Imagine the case where a tech support person tells off an obnoxious  
customer, who takes a picture of the screen.


Furthermore, there are subtle problems with rights-management and  
policy. Let's suppose that I run an organization that needs to  
archive documents. I therefore *must* reject documents that I cannot  
archive.


I have personally stuck more to having crypto be a form of access  
control (once you get to a document, you have it) than as use control  
because:


* The former problem is hard enough
* We know that DRM of any sort will untimately fail
* Human nature will lead people to get into trouble *because* of
  rights management.

I think that the operational issue -- that rights management *cannot*  
work -- trumps everything else, and turns the social issues (if you  
can tell someone off and deny it, will you?) into -- into nothing  
other than a information bomb. You're going to end up looking like  
Wile E. Coyote, with a blackened face and stunned, blinking eyes.


Jon

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