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7z is the new archive format, providing high compression ratio.
The main features of 7z format:
- 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 compression methods are integrated to 7z:
|
Method |
Description |
|---|---|
|
LZMA |
Improved and optimized version of LZ77 algorithm |
|
LZMA2 |
Improved version of LZMA |
|
PPMD |
Dmitry Shkarin's PPMdH with small changes |
|
BZip2 |
Standard BWT algorithm |
|
Copy |
No compression method |
7z also supports filters that improve compression ratio of main compression method. Now the following filters are integrated to 7z:
|
Method |
Description |
|---|---|
|
BCJ |
Converter for x86 executables |
|
BCJ2 |
Converter for x86 executables |
|
ARM64 |
Converter for ARM64 executables |
|
ARMT |
Converter for 32-bit ARM-Thumb executables |
|
ARM |
Converter for 32-bit ARM32 executables |
|
PPC |
Converter for PowerPC executables |
|
SPARC |
Converter for SPARC executables |
|
IA64 |
Converter for IA-64 (Itanium) executables |
|
Delta |
Converter for WAV files |
|
Swap2/Swap4 |
Converters for changing the order of bytes |
LZMA is default and general compression method of 7z format. The main features of LZMA method:
- High compression ratio
- Variable dictionary size (up to 4 GB)
- Compressing speed: about 2-8 MB/s on 4 GHz CPU (2 cpu threads version).
- Decompressing speed: about 30-100 MB/s on 4 GHz CPU (1 cpu thread).
- Small memory requirements for decompressing (depend from dictionary size)
- Small code size for decompressing: about 5 KB
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 code is a part of 7-Zip program distributed under the GNU LGPL. You can download 7-Zip sources and binaries from Download Page.
Major part of 7z code is included to LZMA SDK.
Applications that support 7z archives: WinRAR, PowerArchiver, TUGZip, IZArc.
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