PKZIP is a file archiving computer program, notable for introducing the
popular ZIP file format. PKZIP was first introduced for MS-DOS on the IBM-PC
compatible platform in 1989. Since then versions have been released for a number
of other architectures and operating systems. PKZIP was originally written by
Phil Katz and marketed by his company PKWARE, Inc, with both of them bearing
his initials: 'PK'. History
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. These archives could
optionally be passed through a stream compressor utility, such as compress and
others. Other archivers also appeared during the
1980s, including ARC by System Enhancement Associates, Inc., Rahul
Dhesi's ZOO, Dean W. Cooper's DWC, LHarc by Haruhiko Okomura and Haruyasu
Yoshizaki and ARJ which stands for "Archived by Robert Jung".
The development of PKZIP was first announced in the file SOFTDEV.DOC from
within the PKPAK 3.61 package, stating it would develop a new and yet unnamed
compression program. The announcement had been made following the lawsuit
between SEA and PKWARE, Inc. Although SEA won the suit, it lost the
compression war, as the user base migrated to PKZIP as the compressor of
choice. Led by BBS sysops who refused to accept or offer files compressed as .ARC
files, users began recompressing any old archives that were currently stored in
.ARC format into .ZIP files. The first version was released in 1989
as a DOS command-line tool, distributed under shareware model with a $25US
registration fee. = Version history =
PKZIP PKZIP 0.8 initial version
PKZIP 0.9 supported Reducing algorithm with 4 compression settings and
shrinking. In addition to PKZIP and PKUNZIP, it also included ZIP2EXE, which
required an external self-extracting executable header created by MAKESFX
from the PKZIP executable package. PKZIP 0.92: In addition to bug fixes,
PKZIP included an option to automatically choose the best
compression method for each file. New tools included with PKZIP include
PKZipFix. PKZIP 1.01 added Implode compression,
while Reduced files can only be extracted from ZIP archive. Imploding
was chosen based on the characteristics of the file being compressed. New
utility included Thomas Atkinson's REZIP conversion utility. PKZIP's default
compression behavior was changed from fastest to best. Supported platforms
include OS/2, DOS. PKZIP 1.02 includes new utility
BIOSFIX.COM, which preserved the entire 80386 register set during any mode
switches via INT 15H. OS/2 version added ZIP2EXE and 2 self-extracting archive
headers. PKZIP 1.10: New features included
Authenticity Verification, "mini" PKSFX self-extracting module, integrating
self-extracting module into ZIP2EXE, ability to save & restore volume labels.
Imploding was up to 5X faster and compression ratio was improved over
1.02. EAX register was always saved on 80386 or above CPU. Removed tools
included BIOSFIX, REZIP, MAKESFX. 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". The resulting file format has since become ubiquitous on
Microsoft Windows and on the Internet - almost all files with the .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 supported spanning archives to
multiple disk, which simply split the files into multiple pieces, and using
volume label on each drive to differentiate each other. A new
Authenticity Verification signature format was used. Registered version
included PKUNZJR, PK Safe ANSI, PKCFG utilities.
PKZIP 2.06 was released in 1994. It was a version of PKZIP 2.04g licensed to
IBM. 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 supported
long file names on all builds, and Deflate64 extraction. DCL Implode
extraction was supported on non-DOS ports. A new command-line product was
introduced in Windows 95, OS/2, UNIX platforms, called "PKZIP Command Line",
which featured new command line syntax. PKZIP 2.6 was the last version to
support Windows 3.1 and Windows NT for the Alpha and PowerPC platforms.
PKZIP 2.70 added Email MAPI Support. Registered version included creation of
configurable self-extracted archives, added Authenticity Verification
Information. Distribution Licensed versions included enhanced
self-extractors. Professional Distribution Licensed version could
create Self-Extracting Patch Files, and includes Self-Extractors for Several New
Platforms. PKZIP 4.0 was an updated version of
PKZIP 2.7. Version 3 was skipped as a result of PKZIP 3.0 trojan. It supported
Deflate64 and DCL Implode compression, and the use of X.509 v3
certificate-based authentication., creation of Span or Split large .ZIP
archives. Old PKZIP command line conversion tools were introduced.
On 2001-08-21, PKWARE announced the availability of PKZIP 4.5. PKZIP 4.5
included ZIP64 archives support, which allowed more than 65535 files per ZIP
archives, and storing files larger than 4 gigabytes into .ZIP archive. A version
called PKZIP Suite 4.5 also included 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, which introduced Strong Encryption
Specification 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 compression, with Professional Edition supporting 256-bit
AES. PKZIP 7.0 changed SES to use non-OAEP
key wrapping for compatibility with smart cards and USB tokens. Support of
creating AV authenticity verification archives was dropped. PKZIP could now
create archives of the following types: ZIP, BZIP2, GZIP, TAR, UUEncoded,
XXEncoded. PKZIP 8.0 was released on 2004-04-27. In
addition, PKWARE renamed its PKZip Professional to SecureZIP. Creation of
ZIP archives with encrypted headers was available.
PKZIP 9.0 was the first version to unofficially support Windows Vista.
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.
Desktop PKZIP version was no longer developed beyond version 9.
SecureZIP On 2007-04-24, PKWARE announced the
release of SecureZIP Standard Version 11 as freeware, available on
www.securezip.com. SecureZIP comes with SecureZIP Standard, 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,
FIPS-140 security mode. SecureZIP 12 was released on 2008-2.
SecureZIP 12.1 was released on 2008-06-03 Freeware SecureZIP includes a
free digital certificate and inclusion in the SecureZIP Global Directory. The
certificate was supplied by Comodo. Registration key was changed so keys
from versions 8 or earlier no longer work.
SecureZIP 12.2 introduced SecureZIP Express, while SecureZIP Standard became
shareware. SecureZIP Express did not include the Microsoft Office
integration, but the registration cost was reduced to $19.95. Registration key
was changed so previous keys no longer work.
SecureZIP 12.3 added support of PPMd, LZMA compressions. Desktop version added
Federal Desktop Core Configuration compatibility, 64-bit OS support,
ability to rename a ZIP attachment when sending email, improved support for
Windows Vista dialogs. Enterprise version added expanded support for
setting policy for 64-bit systems. SecureZIP 12.4 was released on
2009-12-14 now supports operation on Windows 7, option to switch to "Office
fluent"-style ribbon GUI, 64-bit edition for use with 64-bit versions of Windows
Vista and Windows 7. SecureZIP 12.5 added integration with
Microsoft Office 2010, custom alternative extensions for mailed .ZIP
archives, extracting WavPack files within ZIP archives, extracting files
from archives created on IBM z/OS using hardware compression tools, changes in
FIPS Mode to support NIST algorithm changes affective end of 2010.
SecureZIP 14 added support to create and extract OpenPGP files, support for
digital time stamping of signed archives, support for processors with
AES-NI instruction for faster AES encryption, ability to extract 7-Zip
files and CD/DVD Data Image files, new Auto Select View, ability to preserve
Zone Identifier information in downloaded files, support to add and
extract NTFS alternate streams, added file search logic.
SecureZIP and PKZIP 15 for z/OS added features to expand offloading
capabilities for z/OS and mainframe hardware, as well as compression
capabilities based on a partnership with IBM.
.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.
Compatibility Although popular at the time, ZIP
archives utilizing PKZIP 1.0 compression methods are now rare, and many modern
unzip tools are unable to handle "shrinking" and "reducing", although
"imploding" is usually supported. Patents
Shrinking uses dynamic LZW, on which Unisys held patents. A patent for the
Reduce Algorithm had also been filed on June 19, 1984, long before PKZIP was
produced. Other products
PKWARE also used its PKZIP standards on following products:
SecureZIP PKZIP Explorer
See also Comparison of file archivers
Comparison of archive formats List of archive formats
References External links
= Official = Official website, PKWARE
PKZIP from PKWARE PKZIP 2.50 for DOS
SecureZIP from PKWARE APPNOTE
= Other = SecureZIP Homepage
Commentary from SEA owner about Phil Katz, the lawsuit, and his death
CONTROVERSY: LAWSUITS: SEA vs. PKWARE Judgment in favor of SEA in SEA v.
PKWARE and Phil Katz How to Use PKZIP From the Command Line