Paul, you are a smart hacker, DPI can not stop you,:-).
DPI hardly can tackle encrypted communication now, but this do not prevent DPI from getting more and more market deployment. Maybe someday,most internet communications will be encrypted to circumvent such kind of inspection, then I think new techonolgies will be devised to face these embarrassment.
Anyway, I think content protection like copyright protection is a interesting area that worth doing something.
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----- 原邮件 ----- 发件人: "Paul E. Jones" paulej@packetizer.com 日期: 星期五, 九月 26日, 2008 下午2:06 主题: RE: RE: [itu-sg16] Q22 Question - SATC 收件人: 'zourong 52447' zou.rong@huawei.com 抄送: ''Noah Luo ' ("罗忠")' noah@huawei.com
Rong,
You are right that current file sharing networks (mostly) do not use encryption. But, they would if necessary. In fact, I have a file sharingprogram on my machine that does offer encryption for file transfers. If such measures were employed to block traffic, I think all tools would simply encrypt contents by default. One could try to guess the contents of the encrypted file by looking at such things as the file length, etc., but nothing is perfect.
I can accept that no solution is perfect, but I honestly believe that this one just will not work in practice. I used to be one of the kids in high school that would remove copy protection from software products by manuallyaltering machine code right on the disk. I even wrote my own utilities to allow me to modify code on disk -- and I wrote that in assembly language. Lawful intercept works for a few reasons:
- Most criminals are stupid and use public communication
- Almost everybody connects to a carrier network to carry voice --
so carriers become a natural intercept point
Lawful intercept does not work for smart criminals. They use secure communication channels.
But, we can't really compare this to Lawful Intercept. Normal users just use the tools that are out on the Internet. If I were writing a file sharing program and encountered packet filtering issues, I would immediatelyemploy encryption. I could write the necessary code in an afternoon and effectively defeat systems employed to stop it. And, those systems are all very expensive hardware-based solutions that would be rendered useless. Honestly, I'm not trying to be an irritant :-) But, I'm quite doubtful that any DPI scheme can work to stop the proliferation of copyrighted material.It's simply too easy to devise a work-around in software and, while the DPI logic can get more complicated, the algorithms in a PC-based application can be revised and updated far more rapidly. Heck, I would even have the packet encoding algorithms written in such a way as to be downloadable when the program starts. That way, the newest encoding algorithms are always available every time the program starts.
Paul
-----Original Message----- From: zourong 52447 [mailto:zou.rong@huawei.com] Sent: Thursday, September 25, 2008 11:48 PM To: Paul E. Jones Cc: 'Noah Luo ' ("罗忠") Subject: 回复:RE: [itu-sg16] Q22 Question - SATC
Paul，
Sorry for taking so long to respond to your mail because I have
taken a
long vacation and then followed by a busy business trip.
I agree with you that the method proposed in my contribution AVD
3541> is not a perfect solution to the copy-right protection issue. It could
not handle the case that the communication is encrypted ?C as you mentioned. In fact, I think it is one of the limitations of DPI technology. The signature-based DPI technology could not inspect the encrypted data flow. But I still believe that it could work and do something
useful in
a broad range of use cases, just like the lawful interception: it hardly could handle the encrypted communication but it still can
work> well.
As to your suspicion whether it could work in a practical
situation.> I hope it could work in some public file sharing scenarios especially
the P2P file sharing. Why I put my effort in study the P2P file
sharing> scenario is that P2P file sharing is the most popular file sharing
tools nowadays and most of the files being shared are multimedia
files> and many of them are pirated.
P2P file sharing has one important character that could be
exploited:> the file information is almost public. It should let people know what
the resource is, for example, the file name, file type, file
size, file
hash value etc., these file describe information will be
transmitted in
the file sharing control messages and could be intercepted by SATC.
Another character of P2P file sharing is that it seldom uses
encrypted> communication because that will bring burden to its efficiency and
affect its popularity.
Then to the question of “good database” and “suspicious database”.
What
I want to do is a multi-level inspection and filter. It maybe
works as
following:
Extracting_file_information(); Searching_good_database(); If(got matched item) { Compare_signature(); If(match) { It is copy-righted file and transmitted; } Else { Searching_suspecious_database(); If(match) { It is a known pirated version, stop it; } Else { It maybe a new pirated version, record it temporality and notify the content provider to make sure and to update the suspicious database ; Transmit_flow(); } } }
In this multi-level filtering, the first level ”good database” filtering can be performed with the help of a reasonably small-
sized> database and achieve rather fast processing speed, the second level
”suspicious database” filtering may require a much bigger
database. But
only searching only a part of them each time also could yield reasonable processing speed.
So that is what I want to do, only those truly pirated file sharing will be stopped right now, other suspected file sharing will be recorded and let the technicians to do further judgment.
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----- 原邮件 ----- 发件人: "Paul E. Jones" paulej@packetizer.com 日期: 星期五, 九月 12日, 2008 上午11:50 主题: RE: [itu-sg16] Q22 Question - SATC 收件人: 'Noah Luo(罗忠)' noah@huawei.com 抄送: zou.rong@huawei.com
Noah,
I have no objection to exploring the idea. But, I'm 100% certain it will not work :-) I am various serious about that. When I was a teenager, I spent a lot of time removing copy protection from software
(actually> > modifying the machine code by hand), hacking computer systems,> > etc. Even
when I was in college, I had a professor who called me an
unscrupulous
hacker. He was only half joking. He had a real admiration
for my
technicalability, but wasn't very happy with some of the
hacking I
used to do. Still, he recognized that I was a good kid who just wanting to explore and learn as much as possible.
I used to play with viruses. I would even write some that would not cause harm -- they would never replicate. Rather, they would just run in the background of machines that I placed them on, loading into the system at boot time. I still have a collection of probably 1,000 virus files, many with the assembly code.
The short of it is that I have a lot of experience at this
sort of
thing.While I don't do the hacking I did when I was a kid, I can guarantee you that there will be some just ready to tackle the challenge of breaking any kind of defense like what this standard intends to provide. And, as I said, the simplest thing to do is simply use TLS. In fact, I could
exchange
pirated music or video via e-mail between my server at home and anybody else who uses TLS -- my servers all use encryption. But, we can certainly employ simpler techniques. For example, I could do this:
K = 256_bit_random_key; while(not_end_of_file) { M = read_file(16 octets of the file); Y = M XOR K; transmit_message(Y); K = rotate_right(K); } transmit_message(K);
This is a very simple and extremely fast encryption algorithm that willactually transmit the session key at the end. So, there
is no
secrethidden, but it avoids the need of exchanging encryption keys some other way. This is not a flawless procedure, though. In fact, this is very easy to "crack", since we're just XORing the bits of the input stream with the key and then rotating the key 1 bit after each message. If an input stream had a number of 0s, then the key would appear as repeated data blocks that can be easily identified by a cryptography person. Heck, even I would recognizethe pattern. But, this might still be complex enough to avoid real-time detection of pirated content. But, I could just as easily use AES
and
*really* encrypt the media and place the 256-bit initialization vector and key at the end of the transmitted media stream :-)
Anyway, like I said-- I have no objections to studying this. I just am just a firm believer that it will only stop the casual pirates: those who want to use gmail.com or something to send an e-mail containing music.
It
would not stop software designed for secure file exchange, either person-
to-
person or across file sharing networks.
My primary concern now is with the wording in the report. Rong felt it was OK, but I still think it's wrong. It says: "... if SATC finds a data stream carrying content failing to match a known signature, it will block the stream or mark it as being
suspicious.”> >
Worded another way, this sentence says: "if the data stream contains an unknown data stream, block the data stream."
Now that would actually work to block pirated content, because you essentially only let known data through the network. But, I don't thinkthat is the intent, and it's definite not what the AVD document said.
Paul
-----Original Message----- From: Noah Luo(罗忠) [mailto:noah@huawei.com] Sent: Thursday, September 11, 2008 5:46 AM To: 'Paul E. Jones' Cc: zou.rong@huawei.com Subject: 答复: [itu-sg16] Q22 Question - SATC
Dear Paul Thank u very much for your good analysis and insightful
comments on
this specific aspect SATC.I will work together with Rong and come up
with a
solution as to how the Q22 meeting report will be appropriatedly reworded.Based on C3541 itself,actually, Q22 meeting report just faithfully reflects the basic idea of the scheme described.But if we
also take
into account the supplementary information Rong provided in his mail
to you,
then Q22 report may need incorporate some more information.
As for your questions regarding the feasibility of using
signature> > > matching
to block pirated contents transmission.I agree that we need more careful consideration.I think it will be ideal if more contributions
will be
submitted by Rong to the next SG16 meeting so that we can
have more
extensive discussion.My personal feeling is that it is a rather innovative idea to use this kind of techniques to block illegally
distributed> > > contents,
but there may still lack some feasible technical points to
enable this
idea to be transformed into a practical solution.
Paul, do you think this arrangement will be okay?
Best Regards
Noah
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-----邮件原件----- 发件人: itu-sg16-bounces@lists.packetizer.com [mailto:itu-sg16-bounces@lists.packetizer.com] 代表 Paul E. Jones 发送时间: 2008年9月11日 10:48 收件人: 'zourong 52447' 抄送: itu-sg16@lists.packetizer.com 主题: Re: [itu-sg16] Q22 Question - SATC
Rong,
I think the meeting report is not exactly correct. The Q22
meeting> > > report
said that SATC would block content that that failed to match a signature. What you said is that SATC would block media content that
matches a
"good" signature, but is apparently altered in some way. That is, it
would
block media that it can clearly identify as pirated content.
So, perhaps we should revise the wording that is presently in
the Q22
meeting report related to AVD-3541. Can you consult Noah on
what the
correct statement should be?
As for whether this will work, I still have doubts. Even
storing> > > signatures
of all current media could be a massive database and, quite
likely, one
that would need to be in memory, as you need real-time (and likely
wire-
speed) access to the signatures.
I have no objection to doing work on this: if you can meet a
particular> business requirement, great. But, I personally think that trying to
match against signatures will not stop any serious pirate. It might
stop the
casual pirate, though.
A data stream of pirated content can be altered in so many ways
that it
would be easy for somebody to create a program to stream pirated content that does not match a signature in the database. I could run
the media
stream through a cipher algorithm, for example. And, I
could even
transmit the cipher key as the last payload of the message: after
all, the
entire file has been delivered! Secrecy wasn't the purpose of the
encryption,> but
merely to disguise what is being transmitted until we've
successfully> bypassed the SATC "detectors".
Perhaps the simplest thing to do, actually, given the wide proliferation of tools like OpenSSL, is to just use TLS between nodes that
want to
transmit pirated content. That provide more-than-acceptable level of encryption.
In any case, I did not intend to bring the work to a halt,
by any
means. But, be cognizant of the fact that this is a very complex
problem and I
seriously doubt you can devise a method that would prevent a
good> > > hacker
from getting around the system. At best, you will only stop the
casual> "pirates". You would not stop serious pirates or popular "file> sharing"
software. Such software would definitely employ techniques
to get
around any detection/blocking logic in the router/switch.
What's more important right now is understanding what should
have been
stated in the meeting report. I do not think this sentence is accurate:
“... if SATC finds a data stream carrying content failing to
match a
known signature, it will block the stream or mark it as being
suspicious.”
Paul
-----Original Message----- From: zourong 52447 [mailto:zou.rong@huawei.com] Sent: Wednesday, September 10, 2008 4:05 AM To: paulej@packetizer.com Cc: itu-sg16@lists.packetizer.com Subject: [itu-sg16] Q22 Question - SATC
Paul, really thanks your's comments, here is the clarification.
- As to the circumventing problem, I really could not say
their is
a perfect way that could not be circumvented. But I don’t
think it is
easy to do so. This scenario is attempted to provide a
tool for
content
provider to prevent their “specially processed” content, i.e.
copy-
righted content from being pirated. It is assumed the
“specially> > > > processed” content have some characteristic information that
would be
destroyed by any piratical actio n such as using a different decoding method, and these
characteristic> > information or “signature” would be provided to SATC system by
content
provider. As to the compress scheme to circumvent, I think the
SATC> > could handle most of the common compress schemes such as winzar,> > winzip, tar etc., but I also think it is impossible the SATC could
handle all compress schemes. 2) The method mentioned in AVD-3541 is not attempted to create
a
database of all pirated media, it’s a database that store the signature of good media especially those most popular
video or
audio> > recently, so the database will keep in a state of acceptable size.
The
periodical updating of the database is necessary just like the
IDS do
to update the anti-virus database. 3) The pirated media database could exist as an subsidiary
database.> > This was not mentioned in the AVD-3541 because I think it maybe too
detail to describe it in a scenario. The file transmitted
will be
suspected as pirated file when satisfied following two points:
(1)
There is a item in the “good media database” that means the
file is a
target of protecting. (2)the signature of the file transmitted
do not
match with that stored in the data base. Then the suspected file could be blocked directly,
or in
a more
prudent way, it could be just marked as suspicious and search
in a
subsidiary “pirated media database” to make sure it is a
existing> > > > pirated version or it maybe a new pirated version and need more
manual
analytical works of content provider. 4) As to the performance problem, I think this kind of
inspection
may have some negative impact on the packet transmission but
may not
as
terrible as thought, in fact, many DPI product in market can
achieve> > 10G to 40G, even 80G throughput, their process capability is
remarkable.
发件人： Paul E. Jones 发送时间： 2008-09-05 10:59:38 收件人： itu-sg16@lists.packetizer.com 抄送： 主题： [itu-sg16] Q22 Question - SATC
Q22 Experts,
While reviewing the Q22 meeting report, I was intrigued
by a
comment related to AVD-3541. This contribution proposes
that SATC
can be used to block illegal content from being transmitted
over
the Internet by examining the media flow and comparing that
media> > > flow (or some signature thereof) against a database. SATC would
then block content as appropriate.
I would like to comment:
I could easily circumvent any such measure, soany such
system would prove to work only temporarily; and 2) While a given copy of a digital copy of some
content, such
as music or a movie, will have a clearly recognizable
signature,
the same media can be “substantially” altered by merely
using a
different encoding method (e.g., a different video codec or compression scheme); and 3) Actually attempting to create a database of all
known> > > > > pirated media, including all variations, would result in the
creation of a massively huge database; and 4) Maintenance of such a database would be a never-
ending> > > > > chore; and
Notwithstanding the foregoing, while such a databasecould> > > be constructed and flows could be examined, inspecting flows in
real-time and trying to positively identify a given flow
is a
monumental task that will result in significantly negative
impact> > > on packet transmission performance, even if a bank of specialized> > > network processors were employed per router or
switch
In short: do we really want to attempt this? While it’s all technically possible (at the risk of turning a 1Gbps pipe
into a
1Kbps pipe), I would argue that it’s not going to work. I
would
be happy to be first in line to write the software
necessary to
circumvent such a system. And I would do it just
because I
can ;-)
Having said that, the meeting report said that, the meeting
report> > > said that “if SATC finds a data stream carrying content failing to
match a known signature, it will block the stream or
mark it as
being suspicious.”
I underlined the text of significance. This suggests
that the
database would only be populated with signatures of
known good
media flows and would only block unrecognized flows. This
seems
different than what I read and understood from AVD-3541.
What the
meeting report suggests would be a simpler problem with a substantially smaller database. So, what was actually
discussed
and decided for SATC? A system that blocks unrecognized
flows or
a system that blocks recognized flows?
Thanks, Paul