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The main features of the 7z format:
- Open architecture
- High compression ratio
- Strong AES-256 encryption
- Ability to use any compression, conversion or encryption method
- Supports files with sizes up to 16000000000 GB
- Unicode file names
- Solid compression
- Archive headers compression
- 7z has an open architecture, so it can support any new compression methods.
The following methods currently are integrated into 7z:
- 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 the default and general compression method of 7z format. The main features of the LZMA method:
- High compression ratio
- Variable dictionary size (up to 4 GB)
- Compression speed: about 1 MB/s on 2 GHz CPU
- Decompression speed: about 10-20 MB/s on 2 GHz CPU
- Small memory requirement for decompression (depends from dictionary size)
- Small code size for decompression: about 5 KB
- Supports multi-threading and P4's hyper-threading
- The LZMA compression algorithm is very suitable for embedded applications. If you want to use LZMA code, you can ask for consultation, custom code programming, and required developer licenses at www.7-zip.org/support.html
7-Zip also supports encryption with
the AES-256 algorithm. This algorithm uses a cipher key with length of 256
bits. To create the key, 7-Zip uses a derivation function based on an SHA-256
hash algorithm. A key derivation function produces a derived key from a text
password defined by the user. To increase the cost of an exhaustive search for
passwords, 7-Zip uses a big number of iterations to produce the cipher key from
the text password.
