7-zip

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7-zip

7ziplogo.svg
Screenshot
The 7-Zip file manager 19.00 under Windows 10
Basic data

developer Igor Pavlov
Publishing year 1999
Current  version 19.00
( February 21, 2019 )
operating system Windows
( Linux , macOS only as p7zip )
programming language C ++
category Data compression program
License LGPL ( Free Software ) with unRAR restriction
German speaking Yes
www.7-zip.org

7-Zip is a free packing program that is licensed under the terms of the LGPL . The development is carried out by the Russian software developer Igor Viktorovich Pawlow, who published the first version of 7-Zip in 1999 and is still actively developing it today (as of spring 2019). 7-Zip is the reference implementation of the Lempel-Ziv-Markow algorithm (LZMA) he developed. In July 2007, 7-Zip was recognized by SourceForge as the best open source project.

Formats

The 7z archive format

By default, 7-Zip creates archives in 7z format with the filename extension .7z . Each archive can contain many directories and files. 7z is basically a pure container format that is open and modular . Safety and data compression functions are implemented using a series of filters connected in series . These then implement, for example, preprocessors , compression algorithms or encryption filters.

All file names are stored in Unicode coding.

Other supported formats

7-Zip also supports a number of compressed and uncompressed archive formats:

Packing and unpacking

The following formats can be unpacked and unpacked:

  • zip (including AES encryption via 256 bit Rijndael, .zip),
  • bzip2 ( .bz2),
  • gzip ( .gz),
  • tar ( .tar),
  • xz (including LZMA2, .xz),
  • wim ( .wim, .swm).

Formats based on zip or gzip:

To compress zip and gzip files, 7-Zip uses a deflate encoder it developed itself, which often delivers better results than the much more frequently used deflate implementation of zlib , although this is at the expense of the compression speed. This version of the deflate encoder is also available independently of 7-Zip as part of the AdvanceCOMP suite.

Just unzip

In addition, archive content or packed data can be extracted from files in the following formats:

  • General purpose archives

7-Zip can .msiopen some Windows Installer files ( ) and offers access to their entire content, including the meta files. Also can be personalized with LZX compressed Microsoft Cabinet files ( .cab) and compressed with LZMA NSIS - installers open. The same applies to some other executable programs (extension for example .exe). 7-Zip can therefore also be used to check whether an unknown binary file is an archive and, if necessary, to extract its content.

  • Compressed individual files
    • compress ( .Z)
    • raw LZMA data streams ( .lzma)
    • MSLZ

Algorithms

The native 7z compression makes use of a variety of algorithms . After sorting the files to be packed in a favorable order and (with progressive compression ) possibly concatenating them into a continuous data stream, certain file types can be processed with various prefilters or preprocessors in order to achieve better results in the subsequent compression. To this end, supported formats appropriate filters as BCJ and BCJ2 for Windows program files are executable files in a row x86 - Machine Code used. Decorrelation, for example, PCM - and raster graphics data is a delta filter available.

For the following main compression step, the native 7z format supports the LZMA, PPMd and bzip2 methods.

An encryption step with AES can then be added.

With the LZMA and pre-filters used by default, better compression rates are achieved than with other popular formats. Especially with large amounts of data, it often clearly outperforms the common RAR .

LZMA

LZMA is a relatively new process developed by Igor Pavlov himself and introduced with 7-Zip. It uses an improved variant of the LZ77 algorithm, Markov chains and a range coder (an implementation of arithmetic coding ) for entropy coding .

Encryption

7-Zip supports AES- standardized 256-bit Rijndael encryption . The encryption can be activated separately for the packed files as well as for the 7z directory structure. If the directory structure is encrypted, the correct password must be entered to display the names of the files contained in the archive.

The WinZip AES encryption standard is also supported so that ZIP archives can be encrypted with 256 bit AES. However, the directory structure cannot be encrypted as is the case with 7z archives.

Functions

7-Zip offers many features, including:

  • The possibility of storing the compressed and archived data in several parts (volumes) with a fixed or dynamically variable size instead of in a single archive. This makes it easier to create backup files on removable media such as CD-RW or writable DVD .
  • Precise setting options for using multiple processors / processor cores / threads .
  • The ability to extract archives with corrupted filename information, renaming the files if necessary.
  • The ability to try and open executable files ( .exe) as archives. In this way, data can be extracted from various installation programs and self-extracting archives without having to run the corresponding program.
  • Self-extracting archives can be created. However, this only works for archives in one file, not for archives with multiple volumes.
  • In 2-panel mode, the program can also be used as a simple "orthodox" file manager (in the style of Norton Commander, for example ).

Embedding in Windows

The graphical user interface can be seamlessly integrated into Windows via “ drag and drop ” and context menus . A command line version and a plug-in for the FAR Manager are included.

When unpacking archive files, 7-Zip (unlike Windows Explorer , WinZip and WinRAR ) does not transfer an existing Zone.Identifier to the extracted files.

Availability for different operating systems

7-Zip is being developed for Windows , but there is also a portable command line version of the program, p7zip , which can be compiled across platforms for the BSDs , Linux , Unix , OS / 2 , BeOS and AmigaOS 4 .

There are many front ends for p7zip , e.g. B. enable integration into graphical user interfaces .

Furthermore, with the XZ Utils, there is a collection of tools based on the LZMA code of the LZMA SDK for pure data compression (i.e. without archiving function), with which the LZMA can be used analogously to programs such as gzip, bzip2 or zlib (for example also in Combination with tar).

7zX is an implementation for macOS , which only has the compression format in common with the version for Windows. The application itself is built on a separate code base .

There are Java - .NET - and Python - bindings .

safety

The installation program of 7-Zip and all self-extracting archives created with 7-Zip had security gaps up to the release of program version 16.00.

The vulnerabilities that u. a. allowed the smuggling and execution of malicious code in archived UDF files have been closed in version 16.00.

See also

Web links

Commons : 7-Zip  album with pictures, videos and audio files

Individual evidence

  1. ↑ www.7-zip.org .
  2. ^ Igor Pavlov: 7-Zip License for use and distribution . 2010. Accessed April 16, 2010. (English)
  3. ↑ SourceForge.net: 2007 Community Choice Awards (English) - page at SourceForge.net ; As of December 31, 2008
  4. ↑ Description of the features of the 7z format (English)
  5. ↑ 7z versus rar: two compression formats (English) - Article at kikizas.net , November 18, 2005
  6. ↑ AES encryption information: Encryption specifications AE-1 and AE-2 on the WinZip website (English)
  7. ↑ 7-Zip Portable - Page at PortableApps.com ; As of July 23, 2010
  8. ↑ FullDisclosure: Executable installers are vulnerable ^ WEVIL (case 7): 7z * .exe allows remote code execution with escalation of privilege
  9. ↑ FullDisclosure: Executable installers are vulnerable ^ WEVIL (case 14): Rapid7's ScanNowUPnP.exe allows arbitrary (remote) code execution
  10. ↑ Rapid7: ScanNow DLL Search Order Hijacking Vulnerability and Deprecation
  11. ↑ heise Security: Unpacker 7-Zip can be misused to execute malicious code. In: Security. Retrieved May 17, 2016 .