Talk:ZIP (file format)/Archive 1

ZIP name origin
Is ZIP the acronym for something ? Because I don't see a meaning of "compression" for any dictionary meanings for "zip". Jay 19:35, 26 Feb 2004 (UTC)


 * No, it's not an acronym. it is meant to conjure up images of the software zipping along at a high rate of speed and finishing its job quickly. In the 1980s, it was common for software to be named in a way that indicated how fast it was.  This is unusual today, since on modern hardware even very inefficient software operates, as far as the end user is concerned, instantaneously, but in the 1980s, people would pay extra money for software that was 20% faster.  I know of at least four different programs available in the 80s that were named "Zip".  (Besides PKZip, the next most well-known is probably Mark Howell's Zip, a predecessor of Frotz.)  However, as far as I'm aware, PKZip was the only one that had anything to do with compression, until gzip came around, and by then the verb "zip", meaning "compress", was already in common use, almost certainly as a direct result of the popularity of PKZip.  --Jonadab 11:56, 28 May 2005‎ (UTC)


 * You don't? How about "zipping something up" as in packaging something? Mrdice 19:36, 2004 Feb 26 (UTC)


 * That usage derives from PKZip, not the other way around. --Jonadab 11:56, 28 May 2005‎ (UTC)


 * When you say "zipping something up" you're talking of computer files and folders. Tell me another object that you can zip as in package. I couldn't find any non-computer usage of zip as "package/compress" from http://dictionary.reference.com/search?q=zip Jay 19:55, 26 Feb 2004 (UTC)


 * When Phil Katz designed his new replacement program for PKARC, his friend and confederate Bob Mahoney (founder of the EXEC-PC BBS in Wisconsin, where Katz lived) suggested naming it "Zip" for two reasons (according to a phone conversation I had with him in spring of 2004): The name "zip" would imply "speed", which would be an advantage over the ARC and other compression formats, and "zip" implied "zipper", giving a slight tinge of sexiness to the whole thing, as in "zipping up" and "unzipping". Katz went with this idea, and thanks Bob Mahoney for coming up with the name in the README file for basically all versions of PKZIP. --Jscott 18:35, 5 Jan 2005 (UTC)


 * Mention should be made, at least here in Talk, of the history behind this, and the reason that Katz was in search of a new file format and a new extension. System Enhancement Associates (SEA), the inventor of the "ARC" format (the first archive format that stored individual compressed files, instead of compressing the whole archive of uncompressed files the way that tar and LBR handle it) sued Katz over his PKARC/PKXARC programs, claiming they violated copyright. They won. Katz got his revenge by making ZIP a public format from the outset, and basically outcompeting SEA into oblivion. --Rpresser 18:56, 19 June 2006 (UTC)


 * Is there any README file on the net which has mention of Bob Mahoney ? Jay 11:18, 18 Jan 2005 (UTC)


 * I looked in a couple of PKZIP distributions (1.02 and 2.04g) and couldn't find any mention of Bob Mahoney. --Zundark 16:14, 18 Jan 2005 (UTC)


 * It is in APPNOTE.TXT. The following is copy-and-pasted from the 2.04g version of that file:

In addition to the above mentioned contributors to PKZIP and PKUNZIP, I would like to extend special thanks to Robert Mahoney for suggesting the extension .ZIP for this software.
 * --Jonadab 11:56, 28 May 2005‎ (UTC)


 * That's strange - my copy of PKZIP 2.04g has no APPNOTE.TXT. But I found an updated version of the file on PKWARE's site, which contains the same acknowledgement. --Zundark 12:57, 28 May 2005 (UTC)


 * Well, in my opinion, I think it's not only an acronym but it also has a meaning, like zipping it up, packing it down... etc.  --Uber-Awesomeness (talk) 13:50, 13 February 2009 (UTC)

Rename to PKZip?
Should this article be at PKZip file format&mdash;or, bettter still IMO, merged with PKZIP&mdash;to distinguish it from other Zip compression formats? --Joe Llywelyn Griffith Blakesley talk contrib 01:34, 2005 Feb 10 (UTC)


 * Merging with PKZIP probably isn't a good idea, as the format is no longer closely tied to the program that first used it. Moving the article to PKZIP file format would go against the principle of using the most common name as the article title - most people just say "zip file" now, not "PKZIP file". What are the other "Zip compression formats" that you want to distinguish it from? --Zundark 09:19, 10 Feb 2005 (UTC)


 * According to APPNOTE.TXT, the name of the format is .ZIP. Dpbjinc (talk) 08:46, 18 February 2009 (UTC)

Encryption?
I know the .ZIP format can implement password protection. When a .ZIP file is made with the password option, what encryption algorithm, if any, is used? --69.234.192.40 08:41, 23 Feb 2005 (UTC)


 * I know that it is a symetric, private-key algorithm, and that cryptanalists generally don't regard it as highly secure, but I do not know the specifics --User:Jonadab


 * I believe you can pick from a defined list —Preceding unsigned comment added by 66.30.92.158 (talk) 02:44, 29 January 2008 (UTC)


 * The original encryption method provided in DOS versions of PKZIP (I think starting with 1.1?) was, as Jonadab said, a symmetric private-key algorithm. It turned out to have a significant flaw which made it possible to decrypt files when only the first few bytes of plaintext were available (as I recall, about 20 were needed, and if less were available it still reduced the key space to be searched for brute forcing.) Furthermore if several files were encrypted using the same key, as was and is common for archive files, the attack was again available.
 * Even without the known plaintext attack, brute force key searching was very rapid; over 99% (255 of 256) of incorrect keys were obvious before generating a single byte of plaintext. (The decryption algorithm starts by crunching the key through several rounds of processing, and if the first byte out of the gate is incorrect, nothing else need be tried.)
 * All details about decryption are in APPNOTE.TXT, and cracking programs for ZIP files are easy to find.
 * Later versions of WinZIP and of other ZIP programs did indeed let you choose more secure encryption methods. --Rpresser 06:30, 8 February 2008 (UTC)

To those who keep insisting on pointing out that ZIP's one-way hash is susceptible to dictionary hacks: that has nothing at all to do with the strength OR WEAKNESS of the encryption. You can use TrueCrypt with Triple-DES/Blowfish/AES/RCMP/ENIGMA/NSA1 encryption all you like. If your password is "password", a dictionary hack is gonna break it! The weakness of XOR or one-time-pad (one-way hash) is not in the strength of the encryption, but in the weakness of key distribution/transmission! Please quit propagating this nonsense. —Preceding unsigned comment added by KirbyWallace (talk • contribs) 05:46, 6 March 2008 (UTC)


 *  A known plaintext attack is NOT the same as a dictionary attack. What you say about dictionary attacks is true. But the portion of the article that you deleted does not talk about them.
 * A dictionary attack is an attack on the key. A known plaintext attack is an attack on the crypttext, WHEN THE KEY IS NOT KNOWN.  The weakness of the algorithm makes it possible to decrypt the file if only a few bytes of the file that was encrypted are known. --Rpresser 21:14, 6 March 2008 (UTC)

NPOV
The section of this article referring to the 'public perception' of Katz after he developed PKZIP, specifically how he was viewed as the victor in a war against an 'evil corporation', is biased. Can citations be given for this generic public perception assertion? Probably not. If so, they should be listed.


 * I can't provide a cite, but I can concur from my memory. The general feeling on the BBSes was that SEA was being the dog in the manger. Katz had much faster software -- again, this was considered very important -- that did much the same job as SEA's ARC; it not only seemed mean-spirited of SEA to try to muscle him out, but also people just wanted to use the better software, which might have become impossible. Rpresser 07:43, 29 October 2006 (UTC)


 * My own memory is many were sympathetic to SEA. SEA published the source so that there would be a platform independent compressed file protocol.  If the reference implementation of of the ARC format tools were in assembler, cross-platform compatibility would be much harder to achieve. Eustace 18:00, 26 April 2007 (UTC)


 * Still the fact that SEA used a compiler and Katz did all this in assembler does have some merit. At least from my point of view. That assembler was used was one of the factors that made the Katz version faster. It also "blows out of the water" the assertion that Katz absconded with the code from SEA. Since the article makes mention of this I think the NPOV tag should be removed. BingoDingo (talk) 18:22, 7 February 2008 (UTC)


 * As the expert for SEA in the lawsuit, I know that not to be true. The majority of the code used by Katz was lifted directly from copyrighted SEA source code, even down to misspellings in comments. His only original work was in the replacement of a relatively small amount of core C code with hand-optimized assembler. This is why Katz lost the lawsuit, consenting to judgment in favor of SEA. --John Navas (talk) 05:07, 20 March 2008 (UTC)

Bad link?
I think this sentence and the embedded link within it should be changed: "WinZIP was among the most popular." to: "WinZip was among the most popular". since the WinZIP version goes to a "start this page" rather than the real article for WinZip. I did it but I've never actually modified a Wiki article, no guts, so no idea if I did it right... --User:Lar (Larry Pieniazek) 19:13, 8 June 2005‎ (UTC)

compression methods other than deflate
anyone know where i can find more info on the other compression methods zip supports? Plugwash 00:29, 18 Jun 2005 (UTC)


 * The three original PKZIP compression methods were "imploding", "shrinking" and "reducing". Details of all the compression methods can be found in appnote.txt. --Zundark 07:28, 18 Jun 2005 (UTC)

ok i didn't spot those the first time i read through that document, they still seem very vague though when compared to say the deflate rfc. Plugwash 13:43, 18 Jun 2005 (UTC)


 * Other compression methods are Deflate64 and BZip2 Bzip2, LZMA (www.7zip.org) has the best compression of them all. Renegadeviking March 10, 2006

Should ZIP be in caps ?
Should every instance of the word ZIP in the article be in uppercase ? They were all in bold as well, I removed that. Jay 15:57, 16 August 2005 (UTC)
 * well pkzip was originally a dos app so .ZIP was originally capitals. OTOH modern zip files usually have it in lower case. its fine by me if you wan't to change it but if you do so remember to do it consistantly through the article and move the page at the same time. Plugwash 17:17, 16 August 2005 (UTC)
 * If page name is ZIP, then yes, I think in all caps. If page name is Zip, then same in body.  It should not be all lowercase in body (with exception of using it as a verb, but that should not appear in the body except to explain the use of the verb).  A quick Google survey suggests usages fairly evenly split between ZIP and Zip, but "zip" is relatively rare except as a verb or as part of a filename. Removing the bolding was a good move. -R. S. Shaw 20:53, 21 August 2005 (UTC)
 * I guess Quuxplusone's argument below answers the question. I did a little search and was able to find Wikipedia talk:Naming conventions (file formats). Maybe we can copy over our vote there and finally come up with a section on file formats in Naming conventions. Jay 22:29, 21 August 2005 (UTC)
 * I've drafted a proposal on the talk page. Could I get some comments on Wikipedia talk:Naming conventions (file formats), please?

move to Zip (file format)
Whist the original file extention may have been all caps because of the limitations of dos i've never seen anywhere else reffer to the format as ZIP when talking about it and all those caps were jarring. i've already changed the page text but i can't do the move myself because the redirect has been edited in the past.
 * Support Philip Baird Shearer 00:12, 20 August 2005 (UTC)
 * Support. – AxSkov ( ☏ ) 11:17, 20 August 2005 (UTC)
 * Support. Fredrik | talk 22:16, 20 August 2005 (UTC)
 * Strongly Oppose. Obviously someone's not a computer geek. :) Besides, precedent is against it: DVI file format ("DeVice-Independent"), M3U and MP3, PLS (file format), SWF ("ShockWave Flash"), COM file ("COMmand"), WAV ("WAVeform"), DOC (computing), and so on. There are a few lower-cased titles of the form .txt, but many of them are just redirects to the real article (e.g. .bmp→Windows bitmap), and most of them start off e.g. "DMG is a disk image format..."  My conclusion: This is an extremely counterintuitive move request. --Quuxplusone 02:07, 21 August 2005 (UTC)
 * Oppose. Quuxplusone has convinced me, by way of examples, that the current title is acceptable. – AxSkov ( ☏ ) 03:30, 21 August 2005 (UTC)
 * Oppose. All caps is good because it stands out as a technical usage; the fact it is not an acronym seems unimportant. Wpedia convention also generally all caps for file extension (except for pages starting with dot). -R. S. Shaw 20:46, 21 August 2005 (UTC)
 * Support. Honestly, as a file extension, if you want to use "ZIP", whatever. But please don't use it as a name in sentence. "MP3" and "SWF", etc., are acronyms, and therefore naturally go in caps. There is no logic, however, behind writing: "open the DOC file," or "it's a WAV file." Saying it's necessary to indicate that it's file type is like saying my own personal name should be capitalized every time it appears in text just so that everyone knows it's actually a name. The whole concept is simply impoverished intellectually. What is hard to understand about "the .doc file," or "the Wav file" I do not know. Similarly, "The Zip format was invented. . ." is much easier on the eyes. Having caps all over the place is jarring, annoying, childish, and illogical. If other articles are written like this, they should be changed also. —Preceding unsigned comment added by 222.148.9.230 (talk) 07:44, 1 February 2008 (UTC)
 * Support. WushuKungfu (talk) 23:14, 14 February 2008 (UTC)

Page not moved
It was requested that this article be renamed but there was no consensus for it to be moved. Paul August &#9742; 21:48, August 24, 2005 (UTC)

Possible reference to Magic number (programming) ?
Has it been considered to mention the presense of "PK" at the beginning of every zip file? -- Lardarse 09:06, 1 December 2005 (UTC)


 * There's nothing terribly magic about it, it's just Phil Katz's initials; and after reading this page and learning that Phil Katz invented the format, I doubt anyone will have trouble figuring out the usage. Rpresser 07:45, 29 October 2006 (UTC)

Added "commanders"
I've added "commanders" among file managers, because I've seen there are only Explorer/Finder type filemanagers, and commanders were not mentioned although they actually started that trend first (DOS had file managers too, and they handled ZIP archives). I must admit that my addition is somewhat clumsily written (I did it in a hurry and I'm not a native English speaker), and perhaps it is also imprecise (for example I'm not sure when exactly NC included ZIP support, and I don't know well the timeline of other Commanders). Therefore it would be nice if someone could look at it and edit to make that paragraph structured better, and perhaps to correct some of informations I've added. --Arny 06:01, 14 February 2006 (UTC)

info-zip
"In 1994 and 1995 Info-ZIP turned a corner, and effectively became the de facto ZIP program"
 * Maybe in the *nix world it did but afaict in the dos/windows world it was pkzip (which was essentially free as long as you didn't mind violating the unenforced shareware terms) and then winzip (again free as long as you didn't mind violating the unenforced shareware terms) which were used (and then later people moved to either the integrated zip support or zip support included in tools for other formats). Plugwash 12:07, 1 October 2006 (UTC)


 * Ok i've just discovered this was added by an anon, as such its getting pulled until someone steps up to defend it. Plugwash 16:21, 1 October 2006 (UTC)

opendocument
"The OpenDocument format usually uses the JAR file format internally, so it can be easily uncompressed and compressed using tools for ZIP files." is there any evidence that its based on jar and not just on normal zip? Plugwash 16:15, 1 October 2006 (UTC)

64 bit
does anyone know what if any zip tools other than pkzip support either pkwares zip64 extentions or thier own 64 bit extentions Plugwash 16:28, 1 October 2006 (UTC)


 * The module zipfile coming with Python 2.5 does. --217.81.255.59 (talk) 21:28, 6 April 2008 (UTC)

Citation needed.
Will some expert kindly provide a source for the section quoted below, so that I can reach my goal of paring down the Citation Needed references on the following page? http://en.wikipedia.org/w/index.php?title=Category:Articles_with_unsourced_statements&from=Z

Tokenizing (Method 7) This method number is reserved. The PKWARE specification does not define an algorithm for it. This is because the format was developed (as a non-proprietary open specification) by a third-party other than PKWARE for specialized usage.[citation needed]

Sincerely, GeorgeLouis 06:24, 29 October 2006 (UTC)


 * Citation provided. It points to a Wikipedia User Talk page, though, which is probably bad form. Rpresser 07:58, 29 October 2006 (UTC)

Thanks. Have you published this anywhere else? Any place at all where it can be looked at by others and vetted? Sincerely, GeorgeLouis 14:11, 29 October 2006 (UTC)


 * Not for me to publish; talk to the person who said it, on his talk page. Rpresser 16:50, 30 October 2006 (UTC)

Actually, referencing a talk page like this isn't just bad form, I believe it's in contravention of the No original research policy (which is a pretty fundamental one). I've taken that reference out, we really need an external source for this sort of thing. We should also get a source for those compression sizes, I hope it wasn't the result of direct experimentation since that would probably be OR as well. Bryan 01:53, 6 November 2006 (UTC)

Has this article been defaced, what with the name bill bummer and inconsistencies with sentences in the intro? 130.234.5.137 22:56, 14 December 2006 (UTC)

NPOV, Windows
'Let the facts speak for themselves'

Use of term 'minimal' (The Least Possible) re. Window's ZIP handling does not conform to NPOV.

Windows ZIP simply cannot be considered minimal as it handles encryption and decompression of various formats, even though it only has one compression method. This is a personal opinion and readers should be left to decide for themselves what is 'minimal' based upon the facts presented. —Preceding unsigned comment added by 82.19.10.112 (talk • contribs) 19:50, 19 January 2007


 * I agree; the word "minimal" is now gone. A citation for the first version of Windows to support "compressed folders" would be useful. --Quuxplusone 02:03, 20 January 2007 (UTC)


 * If this was the only problem can we now remove the NPOV tag? BingoDingo (talk) 18:18, 7 February 2008 (UTC)

An early open specification
I'm kind of amazed that more (or anything?) is not made of the fact that the specification of ZIP file format was made open from first release. If nothing else, it was an early example to a very wide audience of someone explicitly rejecting closed proprietary formats in favor of the public interest. Is there another example of open specifications that everyone uses - and knows they do? Even Microsoft, disliked by PK, has benefitted! At least allude to the benefits of this phenomenom (open specs) with this as the obvious example. Shenme 01:44, 25 January 2007 (UTC)


 * This article does not exist to promote philosophies of open-source (or open-specification, in this case). It is factually relevant that the spec for the format was available from the first release, but nothing should be said with regard to the beneficial effects of doing so outside the context of the ZIP format. Korval 00:31, 10 February 2007 (UTC)


 * At the time there were many widely used open formats. ARC itself was a published spec, although SEA kept its copyright and sued. In the CP/M world, CRUNCH and LBR were both wide open. --Rpresser 06:35, 8 February 2008 (UTC)

Compression methods - size of uncompressed files
When the different compression methods are compared, what's the original size of those uncompressed files? Diz 06:11, 27 April 2007 (UTC)

File icon
Would it be possible to replace the copyrighted PKZIP icon with one from a free icon set? I know PKZIP originated the file type, so that's why I didn't just change it. --Jtalledo (talk) 23:58, 21 June 2007 (UTC)

Way too many examples in first 2 paragraphs
The following is a bit excessive and really needs to be reduced. Do we really need to list all these programs that interpret or implement zip in some way?

Original:
The format was originally designed by Phil Katz for PKZIP. However, many software utilities other than PKZIP itself are now available to create, modify, or open (unzip, decompress) ZIP files, notably WinZip, BOMArchiveHelper, KGB Archiver, PicoZip, Info-ZIP, WinRAR, IZArc, 7-Zip, ALZip, TUGZip, Universal Extractor and Zip Genius. Microsoft has included built-in ZIP support (under the name "compressed folders") in later versions of its Windows operating system. Apple has included built-in ZIP support in Mac OS X 10.3 and later via the BOMArchiveHelper utility.

ZIP files generally use the file extensions ".zip" or ".ZIP" and the MIME media type application/zip. Some software uses the ZIP file format as a wrapper for a large number of small items in a specific structure. Generally when this is done a different file extension is used. Examples of this usage are Java JAR files, id Software .pk3/.pk4 files, package files for StepMania and Winamp/Windows Media Player skins, XPInstall, as well as OpenDocument and Office Open XML office formats. Both OpenDocument and Office Open XML formats use the JAR file format internally, so files can be easily uncompressed and compressed using tools for ZIP files. Google Earth makes use of KMZ files, which are just KML files in ZIP format.

Revised:
The format was originally designed by Phil Katz for PKZIP. However, many software utilities other than PKZIP itself are now available to create, modify, or open (unzip, decompress) ZIP files. Microsoft has included built-in ZIP support (under the name "compressed folders") in Windows XP and later. Apple has included built-in ZIP support in Mac OS X 10.3 and later.

ZIP files generally use the file extensions ".zip" or ".ZIP" and the MIME media type application/zip. The ZIP file format has also been implemented in many programs, usually under a different name.

Perhaps a link to a list of compression programs that use zip can be listed at the bottom of page.

Chapium 23:21, 10 July 2007 (UTC)

Fair use rationale for Image:PKZIPW48x48x32.png
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BetacommandBot 23:27, 13 September 2007 (UTC)

"Compressed folder" problems
Windows' "compressed folder" thing is unable to properly extract some archives, sometimes not extracting all files, or truncating filenames, or even reporting that the zipfile is broken when in fact nothing is wrong with it. Does anyone have a list of all known deficiencies of the "compressed folders", that is all situations that make it mess up? 82.139.85.9 (talk) 13:13, 2 January 2008 (UTC)

POV and sourcing problems
The early history violates WP:NPOV. It repeats Thom Henderson's position in the ARC/PKXARC debate without qualifications. It also does not cite any sources. This page has a lot of old BBS posts on the subject, including some from the principal participants. I think that the posts can be used as sources for what the participants said, but we need to be careful here. Fortunately, there are no WP:BLP issues, since Phil Katz died in 2000. *** Crotalus *** 11:53, 6 January 2008 (UTC)


 * Revised the questioned sentence to mention what many considered to actually be the main issue at the time... AnonMoos (talk) 15:53, 9 February 2008 (UTC)


 * There is no real POV issue here: Katz lost in court, consenting to judgment in favor of SEA. As the expert for SEA in the lawsuit, I know that the majority of the code used by Katz was lifted directly from copyrighted SEA source code, even down to misspellings in comments. His only original work was in the replacement of a relatively small amount of core C code with hand-optimized assembler. --John Navas (talk) 05:42, 20 March 2008 (UTC)

great spread of performance depending on the software
should there be a section about how the resulting ZIP file can vary in size depending on which software was used to generate it?

Just by looking at the benchmarks of ZIP files on http://www.7-zip.org/ is is obvious that .ZIP app1 <> .ZIP app2 210.80.142.30 (talk) 04:44, 7 October 2008 (UTC)

Split ZIP files
Should more mention be made of split ZIP files? It seems that different applications handle split files differently and this has the potential to cause confusion. Including a section on split ZIP files could help to clarify this. —Preceding unsigned comment added by Chris313 (talk • contribs) 15:21, 7 October 2008 (UTC)

Image?
I'd like to upload Apple's .zip icon to Wikipedia and put it side-by-side The Unarchiver's icon. I have one question: What are the copyright ownerships of it? --Uber-Awesomeness (talk) 13:50, 13 February 2009 (UTC)