PKZIP is an archiving tool originally written by Phil Katz and marketed by his company PKWARE, Inc. PKZIP is an acronym for Phil Katz's ZIP program.


File compression routines date back to at least the 1960s: IBM had a compression program called SQUOZE that was commonly used to pack programs on the 709 and 7090 mainframes as part of the SHARE operating system. Previous programs almost certainly existed.

By the 1970s file archiving programs were distributed as standard utilities with operating systems. They include the Unix utilities ar, shar, and tar. These utilities were designed to gather a number of separate files into a single archive file for easier copying and distribution.

During the 1980s, the company System Enhancement Associates (SEA) developed a shareware utility called ARC, based on earlier programs such as tar, that not only grouped files into a single archive file but also compressed them to save disk space, a feature of great importance on early personal computers, where space was very limited and modem transmission speeds were very slow. The archive files produced by ARC had file names ending in ".ARC" and were sometimes called "arc files" as a result.

Later, Phil Katz developed his own shareware utilities, PKARC and PKXARC, to create archive files and extract their contents. These files worked with the archive file format used by ARC, but were faster than ARC. Unlike SEA, which combined archive creation and archive file extraction in a single program, Katz divided these functions among two separate utilities, reducing the amount of memory needed to run them. This also allowed the file extractor to be incorporated into the archive file to create self-extracting archives, which could unpack themselves without requiring an external file extraction utility.

The competition from Katz did not please SEA, who sued Katz for trademark infringement, as well as copyright infringement as it alleged that Katz had plagiarised sections of the code. Katz lost the lawsuit and was forced to pay $62,500 to SEA to cover their legal fees. It was found during the court case that Katz had used SEA's ARC source code for the majority of the application but had only made code optimizations to increase speed. Primarily he changed the word length used by the algorithm from 12 bits to 13 bits resulting in a higher compression for typical binary files. As a result of the lawsuit, Katz changed the names of his utilities to PKPAK and PKUNPAK, and then developed PKZIP and PKUNZIP, which were based on new and different file compression techniques. The suit by SEA angered many shareware users, perceiving that SEA was a "large, faceless corporation" and Katz was "the little guy". In fact, at the time, both SEA and PKWARE were small home-based companies. However, the community largely sided with Katz, and became persuaded by the superior compression capabilities of PKZIP. SEA's ARC was largely abandoned in favor of PKZIP and PKUNZIP as the predominant data compression software on MS DOS.

Other archivers also appeared during the 1980s, including Rahul Dhesi's ZOO, Dean W. Cooper's DWC, and LHarc by Haruhiko Okomura and Haruyasu Yoshizaki.

The first version of PKZIP appeared in 1989. It was a DOS command-line tool and was distributed as shareware with a $25 registration fee.

Version history

PKZIP 0.9 supports Reducing algorithm with 4 compression settings and shrinking.

PKZIP 1.0 supports Shrinking algorithm. Although popular at the time, files in PKZIP 1.0 format are now rare, and many modern unzip tools are unable to handle "shrinking" and "reducing", although "imploding" is usually supported. However, shrinking uses dynamic LZW, which Unisys held patents; the patent for the Reduce algorithm had also been filed on June 19, 1984, long before PKZIP had been produced. [ [ [8 What about patents on data compression algorithms? ] ]

In 1990-3, PKZIP 1.1 was released with a new compression algorithm, colourfully referred to as "imploding", which was chosen based on the characteristics of the file being compressed. [ [ How to Become LZW Free] ] Reducing is supported for expansion only.

In 1993, PKWARE released PKZIP 2.0. This new version dispensed with the miscellaneous compression methods of PKZIP 1.x and replaced them with a single new compression method which Katz called "deflating" (although several compression levels of deflating were provided by the program). The resulting file format has since become ubiquitous on Microsoft Windows and on the Internet - almost all files with the .ZIP (or .zip) extension are in PKZIP 2.x format, and utilities to read and write these files are available on all common platforms. PKZIP 2.x also supports spanning archives to multiple disk, which simply splits the files into multiple pieces, and using volume label on each drive to differentiate each other. A new Authenticity Verification (AV) signature format is used. Registered version includes PKUNZJR, PK Safe ANSI, PKCFG utilities.

PKZIP 2.06 was released in 1994. It is a version of PKZIP 2.04g licensed to IBM. [ [ comp.compression FAQ: What is the latest PKZIP version?] ]

PKZIP 2.50 was the first version released for Windows 3.1, 95, NT platforms. DOS version of PKZIP 2.50 was released on 1999-03-01, as its final MS-DOS product. PKZIP 2.50 supports long file names on all builds, and Deflate64 extraction. DCL Implode extraction is supported on non-DOS ports. A new command-line product is debuted in Windows 95, OS/2, UNIX platforms, called "PKZIP Command Line" (later expanded to "PKZIP Server"), which features new command line syntax.

PKZIP 2.6 is the last version supporting Windows 3.1, Windows NT for DEC Alpha and PowerPC platforms.

PKZIP 2.70 adds Email MAPI (i.e. Send To) Support. Registered version include creation of configurable self-extracted archives, adds Authenticity Verification (AV) Information. Distribution Licensed versions include enhanced self-extractors. Professional Distribution Licensed version can create Self-Extracting Patch Files, and includes Self-Extractors for Several New Platforms.

PKZIP 4.0 is a updated version of PKZIP 2.7. Version 3 was skipped as a result of PKZIP 3.0 trojan. [ [ Malicious Code 101 Definitions and Background] ] It supports Deflate64 and DCL Implode compression, and the use of X.509 v3 certificate-based authentication. [ [ A new look for an old friend: PKZip Suite 4.5] ] , creation of Span or Split large .ZIP archives. Old PKZIP command line conversion tools are introduced.

On 2001-08-21, PKWARE announced the availability of PKZIP 4.5. [ [ PKWARE Improves Efficiency and Security of Internet and Enterprise Network File Distribution] ] PKZIP 4.5 includes ZIP64 archives support, which allows more than 65535 files per ZIP archives, and storing files larger than 4 gibibytes into .ZIP archive. A version called PKZIP Suite 4.5 also includes PKZIP Command Line 4.5, PKZIP Explorer 1.5, PKZIP Attachments 1.1, and PKZIP Plug-In 1.0.

PKZIP 5.0 was announced in 2002 [ [ PKWARE Announces Security-Enabled PKZIP 5.0] ] , which introduced Strong Encryption Specification (SES) for the Professional version of the product, which initially included DES, 3DES, RC2, RC4 encryption formats, and the use of using X.509 v3 certificate-based encryption.

PKZIP 6.0 was released in 2003, which supports BZip2 (based on Burrows-Wheeler transform) compression, with Professional Edition supporting 256-bit AES. [ [,139023447,120271892,00.htm PKZIP Professional Edition 6.0 with Secure Desktop: Secure and compact] ]

PKZIP 7.0 changed SES to use non-OAEP key wrapping. Support of creating AV authenticity verification archives was dropped. PKZIP can now create archives of the following types: ZIP, BZIP2, GZIP, TAR, UUEncoded, XXEncoded.

PKZIP 8.0 was released on 2004-04-27. [ [ PKWare PKZip for Windows 8.0] ] In addition, PKWARE renamed its PKZip Professional to SecureZIP. [ [ PKWARE Releases New Version of PKZIP for Windows] ] Creation of ZIP archives with encrypted headers is available.

PKZIP 9.0 is the first version to unofficially support Windows Vista (as administrator). [ [ PKWARE Responses to Vista Readiness] ] Creation of RC2, DES-encrypted ZIP archives are dropped.

PKZIP 10 Enterprise Edition and SecureZIP 10 were released on i5/OS. It offered the ability to create ZIP64 archives for the target platform. [ [ SecureZIP for i5/OS - FAQs] ] Desktop PKZIP version was no longer developed beyond version 9.

On 2007-04-24, PKWARE announced the release of SecureZIP Standard Version 11 as freeware, available on [ [ PKWARE Announces Free-For-Life Simplified Personal Data Security Software] ] This version supports LZMA compression. SecureZIP comes with SecureZIP Standard (SecureZIP for Windows Desktop), SecureZIP Enterprise, SecureZIP Command Line Interface, SecureZIP for Server, SecureZIP for Server with Directory Integration Module. At this point, only PKZIP for server remained in development. It added UTF-8 file name support, secure exchange of emails and attachments directly from Outlook or Office applications.

SecureZIP 11.2 added SHA-2 hashing (SHA-256, SHA-384, SHA-512 supported), FIPS-140 security mode. [ [ SecureZIP for Windows Desktop v11] ]

SecureZIP 12 was released on 2008-2 [ [ New version of SecureZip] ] .

SecureZIP 12.1 was released on 2008-06-03 [ [ New SecureZIP for Windows Desktop Brings Public Key Cryptography to Every Type of User] ] Freeware SecureZIP includes a free digital certificate and inclusion in the SecureZIP Global Directory. The certificate was supplied by Comodo. [ [,1759,2309854,00.asp SecureZIP Standard Edition for Windows Desktop 12.1] ] Registration key was changed such keys from versions 8 or earlier no longer work.

SecureZIP 12.2 introduced SecureZIP Express, while SecureZIP Standard became shareware. SecureZIP Express does not include the Microsoft Office integration, but the registration cost was reduced to $19.95. Registration key was changed such previous keys no longer work.

.ZIP file format

To help ensure the interoperability of the ZIP format, Phil Katz published the original .ZIP File Format Specification in the APPNOTE.TXT documentation file. PKWARE continued to maintain this document and periodically published updates. Originally only bundled with registered versions of PKZIP, it was later available on the PKWARE site.

The specification has its own version number, which does not necessarily correspond to the PKZIP version numbers, especially with PKZIP 6 or later. At various times, PKWARE adds preliminary features that allows PKZIP products to extract archives using advanced features, but PKZIP products that create such archives won't be available until the next major release.

Other products

PKWARE also used its PKZIP standards on following products:
*PartnerLink (including SecureZIP/PartnerLink, SecureZIP Partner)
*PKZIP Explorer

ee also

*ZIP (file format)
*Comparison of file archivers
*7-Zip works with zip files


External links

* [ PKWARE Homepage]
* [ PKZIP from PKWARE]
* [ PKZIP 2.50 for DOS]
* [ SecureZIP from PKWARE]
* [ SecureZIP Homepage]
* [ Commentary from SEA owner about Phil Katz, the lawsuit, and his death]
** [ Judgment in favor of SEA in "SEA v. PKWARE and Phil Katz"]
* [ How to Use PKZIP From the Command Line]

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Look at other dictionaries:

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  • PKZip — est un programme à la base en ligne de commande créé par Phil Katz et sa société PKWare. Il est composé de PKZIP et de PKUNZIP et permet de compresser et de décompresser les fichiers au format ZIP. Logiciel indispensable dans les années 1980.… …   Wikipédia en Français

  • PKZIP — Тип Архиватор Разработчик Phil Katz  (англ.) Операционная система DOS Последняя версия 2.50 (1 марта 1999) …   Википедия

  • PKZIP — est un programme à la base en ligne de commande créé par Phil Katz et sa société PKWare. Il est composé de PKZIP et de PKUNZIP et permet de compresser et de décompresser les fichiers au format ZIP. Logiciel indispensable dans les années 1980.… …   Wikipédia en Français

  • PKZIP —   [engl. zip »Reißverschluss«], ein Komprimierungsprogramm der Firma PKWARE Inc. in Brown Deer (Wisconsin, USA), mit dem beliebige Dateien komprimiert und in sog. komprimierte Archive verpackt (»gezippt«) werden können. Von PKZIP erzeugte Archive …   Universal-Lexikon

  • PKZip — ▪ software        data compression computer software, used for all types of digital files.       In the 1980s the American software company System Enhancement Associates Inc. (SEA) established a popular software application called ARC, which… …   Universalium

  • PKZIP —    A very popular file compression utility available as shareware. PKZIP not only compresses files to save disk space or cut modem transmission times, but also combines compressed files to create compressed archives.    See also PKUNZIP; WinZip …   Dictionary of networking

  • Pkzip — …   Википедия

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  • Pkzip — ● np. m. ►PACK Grand classique du petit utilitaire mondialement utilisé, permettant d exploiter la compression Zip …   Dictionnaire d'informatique francophone