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RE: [Swftools-common] Could we think about a protection / encryption pro

From: raphael benzazon
Subject: RE: [Swftools-common] Could we think about a protection / encryption process for the swf from pdf2sw
Date: Mon, 5 Nov 2007 05:18:20 +0000


    Thanks Sairam for your answer and advices.

    After trying to understand completely what you explain, i think that maybe i wasn't clear, or i'm not aware of technicals stuffs.
    I don't know how to avoid a file to finish in the browser's "temporary internet files" folder. Since the file is present, the problem for me is not that it will be possible to use my application. It's more the possibility to keep the pages and distribute them for further free reading that disturb me.
    I just found a way finally, by using swfcombine, to add a code that unload the page as soon as it's displayed, when you open it, if it's not loaded in the right "reader". Since the reader has his own protection system, it could do the trick. I wonder if a more drastcal way could be considered. Like putting a kind of encryption in the swf generated by pdf2swf. I beleive the protection from reading isn't available yet in the swf format. Also a swf file that load another, has no way to decrypt the loaded one file while loading it.
    If you want to read a txt file, it's possible to encrypt it and put the decrypter in the swf, after masking the code that decrypt, the security created is acceptable (but easily breakable). but for the swf, no way

    Another way to consider the protection could be to separate the font data and the swf page. So if the swf "reader" has the fonts and is protected, it will be the only way to see the page including the page.

    So pdf2swf could create 2 files instead of 1 : one font file and the other with the rest of the datas.
    Again with swfcombine, we could add a "font" file to the reader as a librairy.
    That way could truly protect the page content integrity while reducing the page file size.

    By the way, does anybody know how to avoid file caching on the client side hard drive for a swf displayed in http? (it's the fastest solution for my problem, even if the bandwith is wasted)


Date: Sun, 4 Nov 2007 18:17:12 -0800
From: address@hidden
To: address@hidden
Subject: Re: [Swftools-common] Could we think about a protection / encryption process for the swf from pdf2swf


I came upon a similar problem once and solved it by automating the pdf->swf process and then using a viewer to dynamically load and display the swf using actionscript. The viewer and server can have matching keys and you can implement simple public-key encryption or something else to be sure that only your viewer/actionscript can load/decrypt the swf, and it will only display the swf if it really comes from your server. Similarly you should ensure the server only delivers content to the actionscript/viewer and not to any other browser request.


On 11/4/07, raphael benzazon <address@hidden> wrote:

   I'm thinking about using pdf2swf to bring magazine pages in a flash application, but i need to be sure that it will be very difficult to backup the page's files and to use them to share the magazine easily. Otherwise, i will be forced to use an installed exe instead of a normal web page with a swf. And it will be a waste of time for the lectors. I'm kind of against installing a program when a solution exist to avoid it.
   The main problem is that these files will be available in the temporary internet file folder. So the best way is to add something in the swf that won't allow someone to see the content without to load it in the proper context ( i can handle the creation of this context in my application ). The problem is that there is no way to add script or to change the structure of the swf while pdf2swf is processing. So maybe it will be interesting to think about for next releases of your program, don't u think?
    I already saw that the swf generated can't be really disassembled in sothink decompiler, the fla that are generated don't show the text correctly, and it's a good point, but if you try to open the orinal swf, it works fine.



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Sairam Suresh
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