Keywords:best compression, best archivation, compression tips, compression 7zip, compression guide, data compression, how to compress data;

7z is a new archive format, providing a high compression ratio.

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 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.
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.

Tips for selecting password length:
Here is an estimate of the time required for an exhaustive password search attack, when the password is a random sequence of lowercase Latin letters.
We suppose that one user can check 10 passwords per second and an organization with a budget of about $1 billion can check 10 billion passwords per second. We also suppose that the processor in use doubles its performance every two years; so, each additional Latin letter of a long password adds about 9 years to an exhaustive key search attack.
The result is this estimate of the time to succeed in an attack:

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