Date: Thu, 04 Sep 2003 00:59:44 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: "Gary W. Swearingen" <underway@comcast.net> Cc: freebsd-chat@freebsd.org Subject: Re: Ugly Huge BSD Monster Message-ID: <3F56F0F0.884D2C3C@mindspring.com> References: <4.3.2.7.2.20030901205127.0337b270@localhost> <4.3.2.7.2.20030901203824.0337c920@localhost> <4.3.2.7.2.20030901205127.0337b270@localhost> <3F553FBF.1010208@potentialtech.com> <3F55A19C.73A1614D@mindspring.com> <2xr82xlu07.82x@mail.comcast.net>
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"Gary W. Swearingen" wrote: > Terry Lambert <tlambert2@mindspring.com> writes: > > Adobe gives away only the viewer. They sell the creation tool, > > and they do not give away source code to the viewer. They guard > > the file format and third party tools via vigorous enforcement > > practices utilizing all tools at their disposal, including the > > DMCA. > > Please explain further. I thought that PDF was a sort of > PostScript-ng, with an unobfuscated (or even documented) file format. > I guess I formed that opinion based on the ability of Ghostscript to > print and view PDF files. Is it based on reverse engineering PDF > files? Do PDF files contain IP protection features? Does Adobe think > its developers and/or users copyright infringers under the DMCA? Yes, PDF files *do* contain IP protection features. These features are based on a (relatively) weak cryptographic key system, and an attributes section on the documents that is voluntarily enforced by a reader. In general, Acrobat Reader will voluntarily enforce these bits, even if the document isn't encrypted, but encryption is further protection, since an encryption-protected document can only be read by an encryption-enabled reader. There is also the ability to password-protect certain bits, as well. These bits control things like whether or not you can print the document, whether you can cut sections of the document to a clipboard, whether or not you can save or edit the document (the Adobe Acrobat writers participates in these protocols, as well), and so on. Setting these bits can be done by "Acrobat Distiller" (a printer driver that prints to PDF files) and by the full-on Adobe Acrobat product itself. Overall, this allows you to send a contract to someone, get it back via FAX with signatures, and know that it's the contract you sent them (as one example). To encryption-enable a reader is relatively trivial (there exist patches to xpdf to support this, but the xpdf authors no longer integrate them, nor do they make them available directly), and involves a shared secret known to both the writers and readers. Adobe developers are bound by a license; likewise users. In the license, you agree to certain terms, which include protecting the Adobe rights in the IP protection systems in the software, and to not reverse engineer them. Adobe has loosened up somewhat on the PDF format itself, but in so doing, they've lost some of their presentation guarantees that they used to be able to make. This loosening up is limited to generation of non-IP-protected content, and reading of such content (in fact, they have a cut-down "Adobe Distiller" called "Acrobat PDF Writer" that they make available for download from their web site, though they make it hard to find, and don't put it as the first thing on their downloads page). -- Terry
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