Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Merciadri Luca wrote: Johannes Wiedersich wrote: Just use a grey-by-dotting watermark for black text, merge the layers and it will be rather difficult to remove the watermark. I did not merge the layers before sending it to them. Problematic? Difficult to judge, since I somehow lost track of what exactly you tried to achieve and what is the nature of the document. If you are simply afraid, that someone would use this document as her/his own work you could watermark the pdf and convert it to a low resolution bitmap (as others have already suggested). If the document was later misused, you could just show your nice, high quality printout without watermarks to prove that you are the real author. Another way might be to hand out that bad quality printout on some special paper, either coloured or with rules and keep the pdf version to yourself. It will be about as difficult to retype/recreate such a document from paper as from retyping it from screen, which was your first choice (disallow printing, allow screen viewing). I think you might have gotten better replies in shorter time, if you had been more explicit and clear about what you try to achieve. - -- Johannes In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. - - Galileo Galilei, physicist and astronomer (1564-1642) -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkvOssIACgkQC1NzPRl9qEVFsgCfVRlKyYWkvwPViEKl1j1mWOVj 7GUAn2knZWl/41ciugK7HRDfXVmKgI62 =18lF -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bceb2c2.6050...@physik.blm.tu-muenchen.de
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Jay Berkenbilt wrote: Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: You might use a password if you wanted to provide complete access for some people and no access for others. For someone who has the password, there is no real protection. I sent some financial documents to a loan officer once as a password-protected PDF. I emailed him the PDF and then left the password on his voicemail. For my purposes, that was sufficient security, and it didn't require any fancy technology or software on his end. Here it is. I wrote this in response to a question from a user of my PDF software, qpdf, which is in debian, but other than a quick mention of a few specific tools, the response is not related to any particular PDF application. Thanks for this really interesting text about this stuff. Really, I learnt some things. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. The weak can never forgive. Forgiveness is the attribute of the strong. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Johannes Wiedersich wrote: Merciadri Luca wrote: Johannes Wiedersich wrote: Just use a grey-by-dotting watermark for black text, merge the layers and it will be rather difficult to remove the watermark. I did not merge the layers before sending it to them. Problematic? Difficult to judge, since I somehow lost track of what exactly you tried to achieve and what is the nature of the document. If you are simply afraid, that someone would use this document as her/his own work That is my main concern, yes. you could watermark the pdf and convert it to a low resolution bitmap (as others have already suggested). If the document was later misused, you could just show your nice, high quality printout without watermarks to prove that you are the real author. Yes. That is what I will do next time (if applicable). I was initially not as much suspicious, and that is why I simply let a mere watermark on each page of the document. Another way might be to hand out that bad quality printout on some special paper, either coloured or with rules and keep the pdf version to yourself. It will be about as difficult to retype/recreate such a document from paper as from retyping it from screen, which was your first choice (disallow printing, allow screen viewing). Nice idea too. I think you might have gotten better replies in shorter time, if you had been more explicit and clear about what you try to achieve. No problem, but I do not like (and want) to express my personal opinion and problems to the _whole_ community. Thanks. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. If it's worth doing, it's worth over-doing. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
My reason is quite complicated, and is really justified. Briefly, one person that I know needs to have some report I wrote, but this person should not be able neither to print it nor to extract content from it, for a simple reason: this person could transmit a part (or the whole) [of the] document to a third party, and this third party should not receive the report from the person who could send it to him (the third party), but the third party wants the other fellow (actually not a fellow to me) to receive the report. Doing it via technical means requires that you be able to formally define and control all the cases you want to rule out (and hopefully leave the remaining cases possible). Can you technically prevent him from passing the whole PDF to someone else? Can you prevent her from taking a photo of her screen? Can you prevent her from printing his screen? ... Once you've solved the above technical problems, you'll have to solve the remaining one: can she still read the document? And to make it more interesting: assuming you can't prevent all of those things from happening: what happens if she does one of them? Assuming she hasn't actively tried to workaround the DRM (e.g. she simply took a photo of the screen or transmitted the whole PDF document), her act were perfectly legal so ... what would happen? Now think about the other route: the one based on the law instead of technology: the legal document can simply describe what she's allowed to do, and that will automatically cover all imaginable ways to circumvent any technological means you could imagine. And if she does break the contract, you can sue her. Don't know about you, but to me, it sounds a lot more useful. Stefan -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/jwv633k3a7b.fsf-monnier+gmane.linux.debian.u...@gnu.org
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Wed, Apr 21 at 15:04, Stefan Monnier penned: Now think about the other route: the one based on the law instead of technology: the legal document can simply describe what she's allowed to do, and that will automatically cover all imaginable ways to circumvent any technological means you could imagine. And if she does break the contract, you can sue her. Don't know about you, but to me, it sounds a lot more useful. Except that most technical people would probably rather hammer a nail through their forehead than go through the pain of suing someone and dealing with the legal system, the paper work, the time involved ... So looking for a technical solution, even one that requires an enormous amount of development time, makes sense. Maybe the development time is actually a bonus, if you're interested in that sort of tinkering already. All of that being said - this entire thread is really a question of security, and security is a process and an approach, not an end result. There is no such thing as a 100% secure system that is also useful, in the same way that there is no such thing as a 100% secure PDF that is also useful. So the real goal is to make the document secure enough for one's purposes, while also making the document usable enough for those purposes. I think there have been a lot of good ideas on this thread for managing that trade-off. -- monique -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100421193947.go30...@mail.bounceswoosh.org
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Stefan's suggestion is interesting, but I know pretty much nothing about the Law: I am doing (CS) engineering studies! Monique Y. Mudama wrote: On Wed, Apr 21 at 15:04, Stefan Monnier penned: Except that most technical people would probably rather hammer a nail through their forehead than go through the pain of suing someone and dealing with the legal system, the paper work, the time involved ... And the financial (and social) cost of such paper work and investigations. So looking for a technical solution, even one that requires an enormous amount of development time, makes sense. Maybe the development time is actually a bonus, if you're interested in that sort of tinkering already. True. All of that being said - this entire thread is really a question of security, and security is a process and an approach, not an end result. There is no such thing as a 100% secure system that is also useful, in the same way that there is no such thing as a 100% secure PDF that is also useful. So the real goal is to make the document secure enough for one's purposes, while also making the document usable enough for those purposes. I think there have been a lot of good ideas on this thread for managing that trade-off. Yes. Your relevant remark should conclude the thread. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. Procrastination is the thief of time. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Merciadri Luca wrote: Johannes Wiedersich wrote: Why would an honest soul ever allow information to be read, but not printed? To maintain honesty? An honest soul (i.e. me, here) has to send some data to some dishonest person. The problem is: either you give data to some dishonest person or you don't give that data to some dishonest person. Tertium non datur. Even with acroread it is possible to print screenshots of the documents. Might be a pain to reconstruct a multipage document, but not impossible. I know, and we all know this. But this needs some determination, because it needs some time. And when such problems arise, one often thinks (or should, at least, think) `Do I really need to copy this using that painful way, to bypass some limitation which is actually imposed to me by an honest person?' This is another aspect of security. There are the technical means, and all the infringements which can be done. But, sometimes, `le jeu n'en vaut pas la chandelle.' FWIW, if you'd like to rely on such a scheme for security by obstacles, you'd have to use something else than pdf. pdf's scheme is broken. That's all. The reason that it is broken for pdfs is that the specifications for pdf are freely available, and thus alternative pdf readers have been developed. Your scheme would require closed specifications and closed software to work. This list, however, is all about free software. - -- Johannes In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. - - Galileo Galilei, physicist and astronomer (1564-1642) -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) iEUEARECAAYFAkvNS+oACgkQC1NzPRl9qEVM2wCfQpAVsTAx7GnbTUminwiqUIlp cm4AlRF4NIAhaaT6neYDcg0rYaXGs+k= =XYrP -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcd4bea.2090...@physik.blm.tu-muenchen.de
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Merciadri Luca wrote: John Hasler wrote: What do you mean by real protection? If they possess a copy that they can read they can print it. It should be obvious that there is nothing you can do to stop them. Not so obvious, simply because if they are using some software that is license-limited, and if they are `beginners' in the field, they might simply never find any way to deal with your document in another fashion than the one you only wanted them to work in. Yeah, and 'beginners' bank robbers can be mislead by not writing bank above the door of banks. - -- Johannes In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. - - Galileo Galilei, physicist and astronomer (1564-1642) -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkvNTPQACgkQC1NzPRl9qEWe1QCfXoPqfFqWriUF+Uju+T0qaxPC 2NcAnRNEFi+kmCojaGjIQmDANar/c5L3 =5LqS -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcd4cf4.6080...@physik.blm.tu-muenchen.de
[OT] Enforcing policies (was: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?)
On Mon, 19 Apr 2010 22:56:05 +0200, Merciadri Luca wrote: Camaleón writes: IANAL, but you can always take the legal path and require that the person you are giving the documents first signs a contract to prevent sharing, extracting or printing data. I know this can sound a bit strict measure but is a very usual method in many companies to prevent data leakage, depending upon the importance of the material they share with another partners. Yes. But what happens if they do not sign? If they do not agree with the terms, then they cannot access the doc. Do you then have any proof that you did not ask/blackmail them to prevent them from signing? In any kind of contract, both parts have to agree the terms. No agreement, no contract. More generally, how can you prove that if they did not sign, it is because of their personal opinion? All of us hold our personal opinions and nobody can force any user to sign any contrat they don't agree. But then the relation between two parts stops there. As I don't know what are all of your specific situation details, I'm also unaware if this kind of agreement is out of place or just fits well within your environment. That is some part of the problem. Note that next year, I will make people sign. I think that in a 18 yr. world with engineering students, students should be more responsible about their duty/ies. In open source world, it is not so uncommom to make people who wants to participate in some aspects of sensitive developing (i.e. fsf) to sign and agree with their terms, regardless the age of the developers (if they are young, they parents have to agree). That is the only way to protect (free) the code. You can enforce a PDF to use DRM *and* activation measures. I have found some e-books that I was not able to open with Linux boxes and forced the user reading it on screen just under windows machines with Acrobat Reader 6. More info here: http://kb2.adobe.com/cps/329/329059.html What you have to ask your boss if this is worth for it as you are imposing many limitations to the person you are lending the document and also, you need a server (and a license of Adobe Content Server) to host the files and manage the DRM licences and restrictions :-/ Thanks. I read it, but this is quite commercial, isn't it? Quite? Full, I'd say :-) But is you who seeks for a comercial solution. Only proprietary tools (Adobe Reader?) enforce the use of the kind of policies you are looking for. Inside open source world is a bit difficult to find programs or tools that make what you are looking for, that is, preventing users to make their own :-) Greetings, -- Camaleón -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/pan.2010.04.20.07.55...@gmail.com
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Johannes Wiedersich johan...@physik.blm.tu-muenchen.de wrote: Even with acroread it is possible to print screenshots of the documents. Might be a pain to reconstruct a multipage document, but not impossible. Been there, done that. An absolute pain. Chris -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4130a7xaf8@news.roaima.co.uk
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Mon, Apr 19, 2010 at 11:17:12PM +0200, Merciadri Luca wrote: Russ Allbery wrote: Ummm, unless I'm missing something I don't see *any* post by Russ in this thread. Ahh! I see from your original post you *also* posted to debian-devel. Normally, the only reason to cross-post is for announcements. http://linux.sgms-centre.com/misc/netiquette.php#xpost -- Chris. == -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100420113129.gb18...@fischer
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Ron Johnson wrote: On 2010-04-19 16:17, Merciadri Luca wrote: The problem is that Windows is a jailed, restricted, dumbed-down environment operated by so many clueless users. It's almost certain that there is the occasional Windows user (and with a user base approaching 10^9, occasional is still a very large absolute figure!) who have the motivation and mental clarity to Google break pdf encryption. / So, you need to ask yourself: (a) Does this colleague run Linux? Nice question. He does not. (b) If so, will he read it with Acroread? / (c) Will he be be motivated enough and clever[0] enough to Google break pdf encryption? Motivated enough, sure. He would have better put all this motivation into the work we had to do in group. Clever, not sure. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. You can't kill two birds with one stone. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Gunnar Wolf wrote: Merciadri Luca dijo [Mon, Apr 19, 2010 at 05:32:51PM +0200]: Thing is, PDF is a printing-oriented format. It is a close descendent of PostScript, a full-fledged programming language, but geared towards printers. The main point that makes PDF a more convenient format is that Acrobat made a big campaign to distribute its PDF reader program. As you say. As you quote, others have told you the PDF-provided security is fake. It is just a flag flipped to tell the reader program to pretty please make life miserable for the user. Yes, but it is often sufficient to prevent _beginners_ from hacking the whole stuff. What do you want to achieve with this _real_ protection you say? See my other messages. I am/was encountering a special situation. Whatever can be displayed on screen can be captured (i.e. with the common PrtScr keybinding in many environments). If you want to distribute material and make it hellish to your users to print it, copy from it or use it in any useful way, why don't you send the document as a .jpg file? With such files (.jpg ones) they can print it directly, can't they? -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. When making your choices in life, do not forget to live. (Samuel Johnson) signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Gunnar Wolf wrote: Russ Allbery dijo [Mon, Apr 19, 2010 at 02:14:21PM -0700]: The reasons not to want a document printed are quite easy to understand, but the mechanism is flawed. / Given the setting you mention, you can just slap a red banner stating Confidential, do not print. If it is on a corporate setting, just state it as a policy - and if somebody fails to comply with the policy, there should be sanctions. That is not for an enterprise stuff (at least if you do not consider the universities as enterprises), but I slapped such a banner (here, this is only a simple watermark). But there are also different ways to remove a watermark... Of course, somebody interested in printing the file will do it. Either by his own means or, like my users, by mailing the techie the document asking him to unprotect it. Or by sticking it on a USB key and taking it off-site to a location they can freely tinker with. Sure. But one hopes the measures to be deterrent! That is one of the only thing we can rely on with a given amount of certitude. As I said on my previous mail: If you don't want it to be printed, distribute in a way that makes it hard to be useful when printed. Sure, but how? (For the next time, if any.) They need(ed) to read it, and it must be sufficiently `high-res.' Don't you trust somebody with social security numbers and salary information? Don't give it to them. No choice. I am not the supervisor of the course. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Jay Berkenbilt wrote: Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: The PDF specification itself recommends using external encryption in this case. From section 7.6.1 of the PDF specification: NOTE: Conforming writers have two choices if the encryption methods and syntax provided by PDF are not sufficient for their needs: they can provide an alternate security handler or they can encrypt whole PDF documents themselves, not making use of PDF security. It is very easy to defeat PDF security in any file that has a blank user password since it is just up to the application to enforce security. Yes, but if you ask for some non-void password, you need to send the password by some way to the receivers. Once they have the password, they can do pretty much they want. So, why would you use a password? I've written a detailed explanation of this which I can dig up and send you if you're interested. Sure. I am very interested in it. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. You cannot escape the responsibility of tomorrow by evading it today. (Abraham Lincoln) signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Johannes Wiedersich wrote: Merciadri Luca wrote: Johannes Wiedersich wrote: Why would an honest soul ever allow information to be read, but not printed? To maintain honesty? An honest soul (i.e. me, here) has to send some data to some dishonest person. The problem is: either you give data to some dishonest person or you don't give that data to some dishonest person. Tertium non datur. Yes, but there are some nuances. Let's take my example: how would you have done this? You need to transmit the document, but the receivers are sufficiently dishonest to print it and to claim they are the authors. Even with acroread it is possible to print screenshots of the documents. Might be a pain to reconstruct a multipage document, but not impossible. I know, and we all know this. But this needs some determination, because it needs some time. And when such problems arise, one often thinks (or should, at least, think) `Do I really need to copy this using that painful way, to bypass some limitation which is actually imposed to me by an honest person?' This is another aspect of security. There are the technical means, and all the infringements which can be done. But, sometimes, `le jeu n'en vaut pas la chandelle.' FWIW, if you'd like to rely on such a scheme for security by obstacles, you'd have to use something else than pdf. pdf's scheme is broken. That's all. And what do you advice? The reason that it is broken for pdfs is that the specifications for pdf are freely available, and thus alternative pdf readers have been developed. Your scheme would require closed specifications and closed software to work. This list, however, is all about free software. Yes, but if I had to use closed specs. with closed softwares, I would have to pay, and what about paying for your own rights?? -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
With such files (.jpg ones) they can print it directly, can't they? They can but if you make lousy quality .jpg maybe they can't. Try 70 dpi and not use some ordinary font. If they print they get messy text hard for scanning. But whatever you do they can always sent .pdf to somebody and if they can read anybody else can. There is no protection, just legal consequences and sometimes you can't proof anything. -- Bye, Goran Dobosevic Hrvatski: www.dobosevic.com English: www.dobosevic.com/en/ Registered Linux User #503414 -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcda12a.9050...@dobosevic.com
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Tue, Apr 20, 2010 at 02:27:39PM +0200, Merciadri Luca wrote: Johannes Wiedersich wrote: Merciadri Luca wrote: Johannes Wiedersich wrote: Why would an honest soul ever allow information to be read, but not printed? To maintain honesty? An honest soul (i.e. me, here) has to send some data to some dishonest person. The problem is: either you give data to some dishonest person or you don't give that data to some dishonest person. Tertium non datur. Yes, but there are some nuances. Let's take my example: how would you have done this? You need to transmit the document, but the receivers are sufficiently dishonest to print it and to claim they are the authors. To be honest that is not a question for debian-user. Maybe you should ask a lawyer. P.S. Please trim your posts. -- Chris. == -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100420135341.ga18...@fischer
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
godo wrote: They can but if you make lousy quality .jpg maybe they can't. Try 70 dpi and not use some ordinary font. If they print they get messy text hard for scanning. But if I had tried such a quality, they would not have been able to read it! But nice proposition. But whatever you do they can always sent .pdf to somebody and if they can read anybody else can. There is no protection, just legal consequences and sometimes you can't proof anything. As you say. That is the biggest problem in this kind of stuff. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. Pleasure in the job puts perfection in the work. (Aristotle) signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Salvo Tomaselli wrote: On Tuesday 20 April 2010 12:16:26 Vincent Lefevre wrote: In my opinion, the more safety checks there are, the more stupid the users become. Without safety they have to be awake and careful to what they are doing. Objectively and theoretically, yes. But, theoretically, many things work better than practically. That is the same scheme (but at another scale) as countries where the State/Nation does not ensure security: in these countries, you need to use self-defense to protect you, actually from the whole system. And? Does it make you more stupid if you have safety checks? I don't think so. Same here: if you need to do something which is potentially risky (because the document you send to other persons might be hacked by them), but necessary (the document needs to be send, because it was asked by a superior authority), you need to defend yourself from others. == I think that this discussion does not enter in the scope of Debian Users' list anymore. We shall then stop here to avoid too much O-T messages to be sent to the mailing list. Thanks everybody. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. If you want a thing done right, do it yourself. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On 2010-04-20 06:58, Merciadri Luca wrote: [snip] So, you need to ask yourself: (a) Does this colleague run Linux? Nice question. He does not. In that case, he should be using Acroread, which means you have little to fear. (b) If so, will he read it with Acroread? / (c) Will he be be motivated enough and clever[0] enough to Google break pdf encryption? Motivated enough, sure. He would have better put all this motivation into the work we had to do in group. Clever, not sure. Seems pretty typical to me... -- Dissent is patriotic, remember? -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcdaf12.9010...@cox.net
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Merciadri Luca dijo [Tue, Apr 20, 2010 at 02:00:13PM +0200]: As you quote, others have told you the PDF-provided security is fake. It is just a flag flipped to tell the reader program to pretty please make life miserable for the user. Yes, but it is often sufficient to prevent _beginners_ from hacking the whole stuff. Yet, you say in your previous reply they would be able to remove the watermark from the document. That is clearly more complicated. Whatever can be displayed on screen can be captured (i.e. with the common PrtScr keybinding in many environments). If you want to distribute material and make it hellish to your users to print it, copy from it or use it in any useful way, why don't you send the document as a .jpg file? With such files (.jpg ones) they can print it directly, can't they? If you distribute an image file in such a fashion it can be read on screen but lacks enough resolution to be good for printing, fewer people will print it. Of course, depends on what you want to achieve, on the nature of the document. -- Gunnar Wolf • gw...@gwolf.org • (+52-55)5623-0154 / 1451-2244 -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100420135402.ga31...@gwolf.org
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Ron Johnson wrote: On 2010-04-20 06:58, Merciadri Luca wrote: [snip] In that case, he should be using Acroread, which means you have little to fear. Seems pretty typical to me... It might be pretty typical, but when considered at another scale than `my scale' (i.e. the comparison with the other groups I had to do in the past); I do not have the habit of dealing with such persons. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. It is possible to be born an aristocrat without ever becoming a gentleman. (Nicholas Ridley) signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Gunnar Wolf wrote: Merciadri Luca dijo [Tue, Apr 20, 2010 at 02:00:13PM +0200]: Yet, you say in your previous reply they would be able to remove the watermark from the document. That is clearly more complicated. Sure, but I think that PDFs are composed `in layers,' aren't they? If `layers' were not merged together, it might still be possible to remove the watermark. If you distribute an image file in such a fashion it can be read on screen but lacks enough resolution to be good for printing, fewer people will print it. Of course, depends on what you want to achieve, on the nature of the document. I will think about it later. This is not in my character to think about stuff I could do to prevent other from harming, globally, but one apparently needs to trust nobody. That is sad to resort to technical means for problems which could be fixed at `human scale.' -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Merciadri Luca wrote: Gunnar Wolf wrote: Merciadri Luca dijo [Tue, Apr 20, 2010 at 02:00:13PM +0200]: Yet, you say in your previous reply they would be able to remove the watermark from the document. That is clearly more complicated. Sure, but I think that PDFs are composed `in layers,' aren't they? If `layers' were not merged together, it might still be possible to remove the watermark. Gunnar did not suggest not to merge the layers, did he? Just use a grey-by-dotting watermark for black text, merge the layers and it will be rather difficult to remove the watermark. - -- Johannes In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. - - Galileo Galilei, physicist and astronomer (1564-1642) -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkvN/zkACgkQC1NzPRl9qEVbgQCfaeFmKH9N6M4sLW0cRoCTTLGB lBcAn3mrhaC5sEGADzJXh0grXtQ38jFn =BFUN -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcdff39.4000...@physik.blm.tu-muenchen.de
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Johannes Wiedersich wrote: Merciadri Luca wrote: Gunnar Wolf wrote: Merciadri Luca dijo [Tue, Apr 20, 2010 at 02:00:13PM +0200]: Yet, you say in your previous reply they would be able to remove the watermark from the document. That is clearly more complicated. Sure, but I think that PDFs are composed `in layers,' aren't they? If `layers' were not merged together, it might still be possible to remove the watermark. Gunnar did not suggest not to merge the layers, did he? He did not, as you said. Just use a grey-by-dotting watermark for black text, merge the layers and it will be rather difficult to remove the watermark. I did not merge the layers before sending it to them. Problematic? -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. A woman is like a cup of tea; you'll never know how strong she is until she boils. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Xavier Vello wrote: Le Tuesday 20 April 2010 01:33:37, Russ Allbery a écrit : There's a configuration option in KPDF (and okular, its KDE4 version) saying obey DRM limitations (unchecked by default). You can activate it, and a tool like kiosk might help to configure the default for a corporation. Thanks for this info. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On 2010-04-20 14:34, Merciadri Luca wrote: Johannes Wiedersich wrote: [snip] Just use a grey-by-dotting watermark for black text, merge the layers and it will be rather difficult to remove the watermark. I did not merge the layers before sending it to them. Problematic? Yup. It regularly bites government agencies who faultily redact FOIA documents. -- Dissent is patriotic, remember? -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bce1961.1090...@cox.net
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Ron Johnson wrote: On 2010-04-20 14:34, Merciadri Luca wrote: [snip] Yup. It regularly bites government agencies who faultily redact FOIA documents. Okay. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: Jay Berkenbilt wrote: Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: The PDF specification itself recommends using external encryption in this case. From section 7.6.1 of the PDF specification: NOTE: Conforming writers have two choices if the encryption methods and syntax provided by PDF are not sufficient for their needs: they can provide an alternate security handler or they can encrypt whole PDF documents themselves, not making use of PDF security. It is very easy to defeat PDF security in any file that has a blank user password since it is just up to the application to enforce security. Yes, but if you ask for some non-void password, you need to send the password by some way to the receivers. Once they have the password, they can do pretty much they want. So, why would you use a password? You might use a password if you wanted to provide complete access for some people and no access for others. For someone who has the password, there is no real protection. I sent some financial documents to a loan officer once as a password-protected PDF. I emailed him the PDF and then left the password on his voicemail. For my purposes, that was sufficient security, and it didn't require any fancy technology or software on his end. I've written a detailed explanation of this which I can dig up and send you if you're interested. Sure. I am very interested in it. Here it is. I wrote this in response to a question from a user of my PDF software, qpdf, which is in debian, but other than a quick mention of a few specific tools, the response is not related to any particular PDF application. The PDF specification allows authors of PDF files to place various restrictions on what you can do with them. These include restricting printing, extracting text and images, reorganizing them, saving form data, or doing various other operations. These flags are nothing more than just a checklist of allowed operations. The PDF consuming application (evince, Adobe Reader, etc.) is supposed to honor those restrictions and prevent you from doing operations that the author didn't want you to do. The PDF specification also provides a mechanism for creating encrypted files. When a PDF file is encrypted, all the strings and stream data (such as page content) are encrypted with a specific encryption key. This makes it impossible to extract data from without understanding the PDF encryption methods. (You couldn't open it in a text editor and dig for recognizable strings, for example.) The whole encryption method is documented in the spec and is basically just RC4 for PDF version 1.4 and earlier, which is not a particularly strong encryption method. PDF version 1.5 added 128-bit AESv2 with CBC, which is somewhat stronger. Those details aren't really important though. The point is that you must be able to recover the encryption key to decrypt the file. Encrypted PDF files always have both a user password and an owner password, either or both of which may be the empty string. The key used to encrypt the data in the PDF is always based on the user password. The owner password is not used at all. In fact, the only thing the owner password can do is to recover the user password. In other words, the user password is stored in the file encrypted by the owner password, and the encryption key is stored in the file encrypted by the user password. That means that it is possible to entirely decrypt a PDF file, and therefore to bypass any restrictions placed on that file, by knowing only the user password. PDF readers are supposed to only allow you to bypass the restrictions if you can correctly supply the owner password, but there's nothing inherent about the way PDF files are structured that makes this necessary. If the user password is set to a non-empty value, neither qpdf nor any other application can do anything with the PDF file unless that password is provided. This is because the data in the PDF file is simply not recoverable by any method short of using some kind of brute force attack to discover the encryption key. The catch is that you can't set restrictions on a PDF file without also encrypting it. This is just because of how the restrictions are stored in the PDF file. (The restrictions are stored with the encryption parameters and are used in the computation of the key from the password.) So if an author wants to place restrictions on a file but still allow anyone to read the file, the author assigns an empty user password and a non-empty owner password. PDF applications are supposed to try the empty string to see if it works as a password, and if it does, not to prompt for a password. In this case, however, it is up to the application to voluntarily honor any of the restrictions imposed on the file. This is pretty much unavoidable: the application must be able to fully decrypt the file in order to display it.
PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Hi, I have written a PDF that I have blocked for printing, etc. Acrobat Reader won't print it, because of the restrictions defined on the PDF file's content. However, KPDF accepts printing it, and extracting content from it, etc., even if these actions are unauthorized with acroread. Is it normal? Thanks. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. Don't try to teach a pig to sing. It doesn't work, and you'll annoy the pig. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Mon, 19 Apr 2010, Merciadri Luca wrote: Hi, I have written a PDF that I have blocked for printing, etc. Acrobat Reader won't print it, because of the restrictions defined on the PDF file's content. However, KPDF accepts printing it, and extracting content from it, etc., even if these actions are unauthorized with acroread. Is it normal? yes. -ishwar -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/pine.gso.4.64.1004190943350.11...@cps155.cps.cmich.edu
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Neil Williams wrote: On Mon, 19 Apr 2010 15:31:30 +0200 Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: Anti-features like locking and password protection are not supported and, if implemented, could make the free software tools appear non-free by restricting the functionality available to the user. In this case, the needs of the user outweigh the restrictive tendencies of the writer of the original format. There are no other formats in Debian (AFAICT) which try to prevent only some documents of that format from being printed. Removal or ignoring the addition of code to support such restrictions is a feature in free software IMHO. All PDF's should be printable by free software. Thanks. I can understand this point of view, but, sometimes, such anti-features can be activated for safety reasons. This is the first time I have to do it, but it was necessary, at least until friday. Thanks, -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. You'll always miss 100% of the shots you don't take. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
I Rattan wrote: On Mon, 19 Apr 2010, Merciadri Luca wrote: yes. Thanks. I assume that this is for the same reason as Mr. Williams pointed out. Are _all_ the free PDF viewers running under Debian in accordance with this principle? -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. As soon as a man is born, he begins to die. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Merciadri Luca schreef: Neil Williams wrote: On Mon, 19 Apr 2010 15:31:30 +0200 Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: Anti-features like locking and password protection are not supported and, if implemented, could make the free software tools appear non-free by restricting the functionality available to the user. In this case, the needs of the user outweigh the restrictive tendencies of the writer of the original format. There are no other formats in Debian (AFAICT) which try to prevent only some documents of that format from being printed. Removal or ignoring the addition of code to support such restrictions is a feature in free software IMHO. All PDF's should be printable by free software. Thanks. I can understand this point of view, but, sometimes, such anti-features can be activated for safety reasons. This is the first time I have to do it, but it was necessary, at least until friday. Pdf anti-features are fake security. Don't trust on them, never. Sjoerd signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Mon, 19 Apr 2010 15:31:30 +0200, Merciadri Luca wrote: I have written a PDF that I have blocked for printing, etc. Acrobat Reader won't print it, because of the restrictions defined on the PDF file's content. However, KPDF accepts printing it, and extracting content from it, etc., even if these actions are unauthorized with acroread. Is it normal? Yes. http://en.wikipedia.org/wiki/Portable_Document_Format#Security_and_signatures Greetings, -- Camaleón -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/pan.2010.04.19.14.05...@gmail.com
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Sjoerd Hardeman wrote: Pdf anti-features are fake security. Don't trust on them, never. And what do you suggest if one wants some real protection _and_ the benefits of a format like PDF? Thanks. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. A good laugh is sunshine in a house. (William Thackery) signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Twas brillig at 17:32:51 19.04.2010 UTC+02 when luca.mercia...@student.ulg.ac.be did gyre and gimble: Pdf anti-features are fake security. Don't trust on them, never. ML And what do you suggest if one wants some real protection _and_ the ML benefits of a format like PDF? Thanks. There is no real protection. -- http://fossarchy.blogspot.com/ pgp9tg98yUrsN.pgp Description: PGP signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Mikhail Gusarov wrote: Twas brillig at 17:32:51 19.04.2010 UTC+02 when luca.mercia...@student.ulg.ac.be did gyre and gimble: Pdf anti-features are fake security. Don't trust on them, never. ML And what do you suggest if one wants some real protection _and_ the ML benefits of a format like PDF? Thanks. There is no real protection. Okay. Simple, but definitive. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Camaleón noela...@gmail.com writes: On Mon, 19 Apr 2010 15:31:30 +0200, Merciadri Luca wrote: I have written a PDF that I have blocked for printing, etc. Acrobat Reader won't print it, because of the restrictions defined on the PDF file's content. However, KPDF accepts printing it, and extracting content from it, etc., even if these actions are unauthorized with acroread. Is it normal? Yes. http://en.wikipedia.org/wiki/Portable_Document_Format#Security_and_signatures Thanks! - -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ - -- If it's too good to be true, then it probably is. -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Processed by Mailcrypt 3.5.8 http://mailcrypt.sourceforge.net/ iEYEARECAAYFAkvMgoQACgkQM0LLzLt8Mhw7wwCgnQvBkp6RMdCGEji5BJighFEZ l0oAoIa8yx1Fn46FtAZmE82/yqN5o2Bx =4kA1 -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87r5mbmn3v@merciadriluca-eee.workgroup
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Mon, Apr 19, 2010 at 10:39:03PM +0700, Mikhail Gusarov wrote: Twas brillig at 17:32:51 19.04.2010 UTC+02 when luca.mercia...@student.ulg.ac.be did gyre and gimble: Pdf anti-features are fake security. Don't trust on them, never. ML And what do you suggest if one wants some real protection _and_ the ML benefits of a format like PDF? Thanks. There is no real protection. -- http://fossarchy.blogspot.com/ This is one of the reasons why people who seek to use DRM will not allow their software to be made for Free Software Platforms. DRM is not in the best interest of the users/re-users of content. And by adding DRM, you tell the user that he/she did not buy the content but is renting it until you decide otherwise. People have proven, again and again, that they are capable of circumventing DRM, so it is not an issue of 'if' they will break DRM but when. And it only hinders legitimate user of your content, those who wish to follow these restrictions. From my recollection, KPDF has an option to 'enable' the compliance with the 'do not print' feature. But it is not enabled by default. -- | .''`. == Debian GNU/Linux == | http://kevix.myopenid.com | | : :' : The Universal OS| mysite.verizon.net/kevin.mark/ | | `. `' http://www.debian.org/ | http://counter.li.org [#238656]| |___`-Unless I ask to be CCd, assume I am subscribed _| -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100419164528.gd5...@horacrux
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Vincent Danjean wrote: On 19/04/2010 17:32, Merciadri Luca wrote: If you have free software (ie software you have the sources and are able to recompile) and if you can get the information on the screen, then it is only a matter of programmation to be able to have it on printer. So, free software readers that forbid printing can be (more or less) easily circumvented (and the patch to do this will be done and available on internet). So why would the authors of such readers want to program this at first time. If you want to avoid printing, you need to fully control the whole chain (ie TPA, ...) AND the terminals (ie, if you can show it on screen, some classic 'print-screen-to-file' and graphical software can be used to print the document, or even camera and image post-processing). For now, the only domain where such restrictions works partially are HD-DVD (and its possible it is already broken). This is possible because it is expensive to acquire good quality video data (ie recording what is diffused by a secure HD player on screen by a camera will have no really good quality). This would not work for audio data (at least, until the decoder is not embedded into brain ;-) ) because it would be easy to reacquire good quality data from a line-out. Thanks for this great explanation. So, what would be the use case to allow a someone to read the information but not print it ? In any case, printing it would be more or less convenient but it will always be possible if it is displayed on screen (even with Acrobat Reader) My reason is quite complicated, and is really justified. Briefly, one person that I know needs to have some report I wrote, but this person should not be able neither to print it nor to extract content from it, for a simple reason: this person could transmit a part (or the whole) [of the] document to a third party, and this third party should not receive the report from the person who could send it to him (the third party), but the third party wants the other fellow (actually not a fellow to me) to receive the report. I know that it is _always_ possible (with some determination) to extract content, by some way, of a PDF (even if screenshots were to never work, you can still use a camera). Principally, the most important aspects of such security features are that they are tricky (for some users only, I agree) to unlock, and that they are consequently repulsive at prima facie. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Kevin Mark wrote: On Mon, Apr 19, 2010 at 10:39:03PM +0700, Mikhail Gusarov wrote: This is one of the reasons why people who seek to use DRM will not allow their software to be made for Free Software Platforms. DRM is not in the best interest of the users/re-users of content. And by adding DRM, you tell the user that he/she did not buy the content but is renting it until you decide otherwise. People have proven, again and again, that they are capable of circumventing DRM, so it is not an issue of 'if' they will break DRM but when. And it only hinders legitimate user of your content, those who wish to follow these restrictions. / From my recollection, KPDF has an option to 'enable' the compliance with the 'do not print' feature. But it is not enabled by default. And I consider this as a normal default setting. The problem is that, in my situation [see messages before, please], I _had_ to do this, even if this is not the kind of things I like to do. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Sven Arvidsson wrote: On Mon, 2010-04-19 at 15:52 +0200, Merciadri Luca wrote: At least Evince can be convinced to provide this feature, if you toggle /apps/evince/override_restrictions No problem. Thanks. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Bernd Eckenfels wrote: In article 4bcc77a3.9080...@student.ulg.ac.be you wrote: It is simply not possible to publish something and protect it. The best protection in that case is reputation. Please read my other message, which explains the situation I am/was facing. On the mere principle, I totally agree with you. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
2010/4/19 Merciadri Luca luca.mercia...@student.ulg.ac.be: I know that it is _always_ possible (with some determination) to extract content, by some way, of a PDF (even if screenshots were to never work, you can still use a camera). Principally, the most important aspects of Or paper and pencil. such security features are that they are tricky (for some users only, I agree) to unlock, and that they are consequently repulsive at prima facie. I know that for some cases this 'restriction through inconvenience' is sufficient in practice, but this should not be achievable with free software, even if legitimate. A suggestion: be physically present when that person examine the file, and threaten him or her with violence at a mere attempt of data recording. (But you still face the problem of memory, that is fortunately harder to overcome) -- Elias Gabriel Amaral da Silva tolkiend...@gmail.com -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/s2kda2c618b1004191035yb924db9iafa0bd119bd3d...@mail.gmail.com
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Sjoerd Hardeman wrote: Pdf anti-features are fake security. Don't trust on them, never. Merciadri Luca writes: And what do you suggest if one wants some real protection _and_ the benefits of a format like PDF? Thanks. What do you mean by real protection? If they possess a copy that they can read they can print it. It should be obvious that there is nothing you can do to stop them. -- John Hasler -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87sk6rfj8o@thumper.dhh.gt.org
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Merciadri Luca wrote: Mikhail Gusarov wrote: Twas brillig at 17:32:51 19.04.2010 UTC+02 when luca.mercia...@student.ulg.ac.be did gyre and gimble: Pdf anti-features are fake security. Don't trust on them, never. ML And what do you suggest if one wants some real protection _and_ the ML benefits of a format like PDF? Thanks. There is no real protection. Okay. Simple, but definitive. The real protection would be not to send that information. Why would an honest soul ever allow information to be read, but not printed? Even with acroread it is possible to print screenshots of the documents. Might be a pain to reconstruct a multipage document, but not impossible. -- Johannes In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. - Galileo Galilei, physicist and astronomer (1564-1642) -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcc9735.90...@physik.blm.tu-muenchen.de
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
James Zuelow wrote: That's not a technical problem, it's a management problem. I totally agree. If you can't trust this person to not forward information when he shouldn't, then they should not be involved. _should_. But I am not the person who decides. I am not neither the professor nor the lecturer. This goes for employment, student projects, a TA that might send test questions to students, or anything else. Totally agree. Trust is something you can't enforce with technical means. Such technical means are, for me, only interesting when the problem cannot be fixed in a human way. Perhaps your colleague doesn't understand the importance of being trustworthy with data. Which is too bad for him no matter what field he gets into after school. Precisely, but I had to deal with the facts: a decision had to be taken, and when - you cannot speak to persons because of their `bad faith' (I do not know how you say this in English, actually, that means that one always give a distorted point of view about everything on a given subject), and - you cannot be understood by supervisors, etc., you need to act alone, and that is why technical means are sometimes useful. I do not say that such a situation couldn't be fixed by natural ways (i.e. speaking, etc.), but I say that when you need to act alone, and that time is running out, technical means sometimes deserve their interest. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. Love doesn't make the world go round. Love is what makes the ride worthwhile. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Elias Gabriel Amaral da Silva wrote: 2010/4/19 Merciadri Luca luca.mercia...@student.ulg.ac.be: Or paper and pencil. That needs some determination. I know that for some cases this 'restriction through inconvenience' is sufficient in practice, but this should not be achievable with free software, even if legitimate. For free softwares, not. *By* free softwares, it is already more disputable, but, to me, such softwares should not be able, by essence, to condemn, in some way, one's liberty (even if this liberty only resides in the ability to do pretty much what you want with a given document). A suggestion: be physically present when that person examine the file, and threaten him or her with violence at a mere attempt of data recording. Acting this way might create other problems! But, objectively, this is one way to be sure about it. (But you still face the problem of memory, that is fortunately harder to overcome) True. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. Better is the enemy of good. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
John Hasler wrote: Sjoerd Hardeman wrote: Merciadri Luca writes: What do you mean by real protection? If they possess a copy that they can read they can print it. It should be obvious that there is nothing you can do to stop them. Not so obvious, simply because if they are using some software that is license-limited, and if they are `beginners' in the field, they might simply never find any way to deal with your document in another fashion than the one you only wanted them to work in. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Johannes Wiedersich wrote: Merciadri Luca wrote: The real protection would be not to send that information. I was not able to do it, because of `human' and organizational reasons. I had no choice! Why would an honest soul ever allow information to be read, but not printed? To maintain honesty? An honest soul (i.e. me, here) has to send some data to some dishonest person. Even with acroread it is possible to print screenshots of the documents. Might be a pain to reconstruct a multipage document, but not impossible. I know, and we all know this. But this needs some determination, because it needs some time. And when such problems arise, one often thinks (or should, at least, think) `Do I really need to copy this using that painful way, to bypass some limitation which is actually imposed to me by an honest person?' This is another aspect of security. There are the technical means, and all the infringements which can be done. But, sometimes, `le jeu n'en vaut pas la chandelle.' -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. A loaded wagon makes no noise. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Mon, 19 Apr 2010 18:47:02 +0200, Merciadri Luca wrote: Vincent Danjean wrote: (...) So, what would be the use case to allow a someone to read the information but not print it ? In any case, printing it would be more or less convenient but it will always be possible if it is displayed on screen (even with Acrobat Reader) My reason is quite complicated, and is really justified. Briefly, one person that I know needs to have some report I wrote, but this person should not be able neither to print it nor to extract content from it, for a simple reason: this person could transmit a part (or the whole) [of the] document to a third party, and this third party should not receive the report from the person who could send it to him (the third party), but the third party wants the other fellow (actually not a fellow to me) to receive the report. IANAL, but you can always take the legal path and require that the person you are giving the documents first signs a contract to prevent sharing, extracting or printing data. I know this can sound a bit strict measure but is a very usual method in many companies to prevent data leakage, depending upon the importance of the material they share with another partners. I know that it is _always_ possible (with some determination) to extract content, by some way, of a PDF (even if screenshots were to never work, you can still use a camera). Principally, the most important aspects of such security features are that they are tricky (for some users only, I agree) to unlock, and that they are consequently repulsive at prima facie. You can enforce a PDF to use DRM *and* activation measures. I have found some e-books that I was not able to open with Linux boxes and forced the user reading it on screen just under windows machines with Acrobat Reader 6. More info here: http://kb2.adobe.com/cps/329/329059.html What you have to ask your boss if this is worth for it as you are imposing many limitations to the person you are lending the document and also, you need a server (and a license of Adobe Content Server) to host the files and manage the DRM licences and restrictions :-/ Greetings, -- Camaleón -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/pan.2010.04.19.18.40...@gmail.com
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On Mon, 19 Apr 2010, Merciadri Luca wrote: Vincent Danjean wrote: My reason is quite complicated, and is really justified. Briefly, one person that I know needs to have some report I wrote, but this person should not be able neither to print it nor to extract content from it, for a simple reason: this person could transmit a part (or the whole) [of the] document to a third party, and this third party should not receive the report from the person who could send it to him (the third party), but the third party wants the other fellow (actually not a fellow to me) to receive the report. I know that it is _always_ possible (with some determination) to extract content, by some way, of a PDF (even if screenshots were to never work, you can still use a camera). Principally, the most important aspects of such security features are that they are tricky (for some users only, I agree) to unlock, and that they are consequently repulsive at prima facie. Life is simpler than that: pdf -postscript -print So, do not make the report available!! -ishwar -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/pine.gso.4.64.1004191512050.11...@cps155.cps.cmich.edu
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
I Rattan wrote: On Mon, 19 Apr 2010, Merciadri Luca wrote: Life is simpler than that: pdf -postscript -print So, do not make the report available!! I had thought about it, but the guy won't think about it, fortunately. But you're right. There are many ways for this. Thanks. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Camaleón noela...@gmail.com writes: On Mon, 19 Apr 2010 18:47:02 +0200, Merciadri Luca wrote: Vincent Danjean wrote: (...) So, what would be the use case to allow a someone to read the information but not print it ? In any case, printing it would be more or less convenient but it will always be possible if it is displayed on screen (even with Acrobat Reader) My reason is quite complicated, and is really justified. Briefly, one person that I know needs to have some report I wrote, but this person should not be able neither to print it nor to extract content from it, for a simple reason: this person could transmit a part (or the whole) [of the] document to a third party, and this third party should not receive the report from the person who could send it to him (the third party), but the third party wants the other fellow (actually not a fellow to me) to receive the report. IANAL, but you can always take the legal path and require that the person you are giving the documents first signs a contract to prevent sharing, extracting or printing data. I know this can sound a bit strict measure but is a very usual method in many companies to prevent data leakage, depending upon the importance of the material they share with another partners. Yes. But what happens if they do not sign? Do you then have any proof that you did not ask/blackmail them to prevent them from signing? More generally, how can you prove that if they did not sign, it is because of their personal opinion? That is some part of the problem. Note that next year, I will make people sign. I think that in a 18 yr. world with engineering students, students should be more responsible about their duty/ies. I know that it is _always_ possible (with some determination) to extract content, by some way, of a PDF (even if screenshots were to never work, you can still use a camera). Principally, the most important aspects of such security features are that they are tricky (for some users only, I agree) to unlock, and that they are consequently repulsive at prima facie. You can enforce a PDF to use DRM *and* activation measures. I have found some e-books that I was not able to open with Linux boxes and forced the user reading it on screen just under windows machines with Acrobat Reader 6. More info here: http://kb2.adobe.com/cps/329/329059.html What you have to ask your boss if this is worth for it as you are imposing many limitations to the person you are lending the document and also, you need a server (and a license of Adobe Content Server) to host the files and manage the DRM licences and restrictions :-/ Thanks. I read it, but this is quite commercial, isn't it? - -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ - -- If you want a thing done right, do it yourself. -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Processed by Mailcrypt 3.5.8 http://mailcrypt.sourceforge.net/ iEYEARECAAYFAkvMw2UACgkQM0LLzLt8Mhw3VQCdG8Y7rAFoKnWhTjP8YX4R7INy o0MAn3qK3cQX2ljkTSyYbF4A1OGL/Pkk =uY70 -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87tyr75fh6@merciadriluca-eee.workgroup
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Russ Allbery wrote: I think people are not understanding why users use this feature in some environments. / Yes, sometimes it's a misguided attempt at DRM, but I've more often seen it inside a workplace as defense in depth against *mistakes*. One might, for instance, mark a document as not printable because it contains social security numbers and salary information and it's corporate policy not to create hard copies of the document beause of the risk of exposure of personal information that might put the company at legal risk. Good example. That's not to say that Debian PDF viewers should support this the way that Acrobat does, but for that use case, the desired UI is probably something like a dialog box that pops up and says that the document author has marked this PDF as not printable and asking the user if they're sure they want to override. For this use case, such a warning would probably serve the same purpose. (It may well be that some PDF viewers in Debian already implement such a dialog.) Nice idea, really. That is a good compromise. -- Merciadri Luca See http://www.student.montefiore.ulg.ac.be/~merciadri/ I use PGP. If there is an incompatibility problem with your mail client, please contact me. signature.asc Description: OpenPGP digital signature
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
On 2010-04-19 16:17, Merciadri Luca wrote: Russ Allbery wrote: I think people are not understanding why users use this feature in some environments. / Yes, sometimes it's a misguided attempt at DRM, but I've more often seen it inside a workplace as defense in depth against *mistakes*. One might, for instance, mark a document as not printable because it contains social security numbers and salary information and it's corporate policy not to create hard copies of the document beause of the risk of exposure of personal information that might put the company at legal risk. Good example. The problem is that Windows is a jailed, restricted, dumbed-down environment operated by so many clueless users. It's almost certain that there is the occasional Windows user (and with a user base approaching 10^9, occasional is still a very large absolute figure!) who have the motivation and mental clarity to Google break pdf encryption. So, you need to ask yourself: (a) Does this colleague run Linux? (b) If so, will he read it with Acroread? (c) Will he be be motivated enough and clever[0] enough to Google break pdf encryption? [0] You know society is doomed when Googling is considered clever. -- Dissent is patriotic, remember? -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bcccfd7.1050...@cox.net
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Merciadri Luca dijo [Mon, Apr 19, 2010 at 05:32:51PM +0200]: Pdf anti-features are fake security. Don't trust on them, never. And what do you suggest if one wants some real protection _and_ the benefits of a format like PDF? Thanks. Thing is, PDF is a printing-oriented format. It is a close descendent of PostScript, a full-fledged programming language, but geared towards printers. The main point that makes PDF a more convenient format is that Acrobat made a big campaign to distribute its PDF reader program. As you quote, others have told you the PDF-provided security is fake. It is just a flag flipped to tell the reader program to pretty please make life miserable for the user. What do you want to achieve with this _real_ protection you say? Whatever can be displayed on screen can be captured (i.e. with the common PrtScr keybinding in many environments). If you want to distribute material and make it hellish to your users to print it, copy from it or use it in any useful way, why don't you send the document as a .jpg file? Greetings, -- Gunnar Wolf • gw...@gwolf.org • (+52-55)5623-0154 / 1451-2244 -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100419225344.gf29...@gwolf.org
Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?
Merciadri Luca luca.mercia...@student.ulg.ac.be wrote: Sjoerd Hardeman wrote: Pdf anti-features are fake security. Don't trust on them, never. And what do you suggest if one wants some real protection _and_ the benefits of a format like PDF? Thanks. The PDF specification itself recommends using external encryption in this case. From section 7.6.1 of the PDF specification: NOTE: Conforming writers have two choices if the encryption methods and syntax provided by PDF are not sufficient for their needs: they can provide an alternate security handler or they can encrypt whole PDF documents themselves, not making use of PDF security. It is very easy to defeat PDF security in any file that has a blank user password since it is just up to the application to enforce security. I've written a detailed explanation of this which I can dig up and send you if you're interested. -- Jay Berkenbilt q...@debian.org -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20100419204257.0890259570.qww314...@soup
