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7z Format
- -7z is the new archive format, providing high compression ratio.
- -The main features of 7z format:
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- Open architecture -
- High compression ratio -
- Strong AES-256 encryption -
- Ability of using any compression, conversion or encryption method -
- Supporting files with sizes up to 16000000000 GB -
- Unicode file names -
- Solid compressing -
- Archive headers compressing -
7z has open architecture, so it can support any new compression methods. -Now the following methods are integrated to 7z:
- -| Method | Description |
|---|---|
| LZMA | Improved and optimized version of LZ77 algorithm |
| PPMD | Dmitry Shkarin's PPMdH with small changes |
| BCJ | Converter for 32-bit x86 executables |
| BCJ2 | Converter for 32-bit x86 executables |
| BZip2 | Standard BWT algorithm |
| Deflate | Standard LZ77-based algorithm |
LZMA is default and general compression method of 7z format. The main features of LZMA method:
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- High compression ratio -
- Variable dictionary size (up to 4 GB) -
- Compressing speed: about 1 MB/s on 2 GHz CPU -
- Decompressing speed: about 10-20 MB/s on 2 GHz CPU -
- Small memory requirements for decompressing (depend from dictionary size) -
- Small code size for decompressing: about 5 KB -
- Supporting multi-threading and P4's hyper-threading -
LZMA compression algorithm is very suitable for embedded applications. -LZMA is released under the terms of the GNU LGPL. LZMA is also -available under a proprietary license for those who can not use the GNU LGPL in -their code. If you want to use LZMA code, you can ask consultations, -custom code programming and required developer licenses -from page for support: -Send message to LZMA developer. -Check also information about LZMA SDK.
- -7-Zip also supports encryption with AES-256 algorithm. -This algorithm uses cipher key with length of 256 bits. To create that key 7-Zip -uses derivation function based on SHA-256 hash algorithm. -A key derivation function produces a derived key from text password defined by user. -For increasing the cost of exhaustive search for passwords 7-Zip uses big number -of iterations to produce cipher key from text password.
- -7z is a part of 7-Zip program distributed under the GNU LGPL. -You can download 7-Zip sources and binaries from Download Page.
- -Applications that support 7z archives: WinRAR, PowerArchiver, TUGZip, IZArc.
- -Links:
- - -Copyright (C) 2008 Igor Pavlov.
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