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5 <TITLE>7z Format</TITLE>
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13 <TR><TD><IMG width=110 height=63 src="/7ziplogo.png" alt="7-Zip" border=0></TD></TR>
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16 <TR><TD><A href="./" class="MenuLink">Home</A></TD></TR>
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17 <TR><TD><SPAN class="MenuCurrent">7z Format</SPAN></TD></TR>
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18 <TR><TD><A href="sdk.html" class="MenuLink">LZMA SDK</A></TD></TR>
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33 <A href="http://7-zip.hit.bg/">Bulgarian</A><BR>
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34 <A href="http://7z.sparanoid.com/">Chinese Simpl.</A><BR>
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36 <A href="http://www.7-zip.de/">German</A><BR>
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41 <A href="http://www.7zip.gen.tr/">Turkish </A><BR>
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42 <A href="http://7-zip.org.ua/">Ukrainian</A><BR>
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50 <P><B>7z</B> is the new archive format, providing high compression ratio.</P>
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52 <P>The main features of <B>7z</B> format:</P>
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54 <LI>Open architecture
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55 <LI>High compression ratio
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56 <LI>Strong AES-256 encryption
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57 <LI>Ability of using any compression, conversion or encryption method
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58 <LI>Supporting files with sizes up to 16000000000 GB
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59 <LI>Unicode file names
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60 <LI>Solid compressing
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61 <LI>Archive headers compressing
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64 <P><B>7z</B> has open architecture, so it can support any new compression methods.
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65 Now the following methods are integrated to <B>7z</B>:</P>
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67 <TABLE cellspacing ="2" cellpadding ="4">
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68 <TR> <TH class="Title" width="60">Method</TH> <TH class="Title">Description</TH></TR>
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69 <TR> <TD class="Item">LZMA</TD> <TD class="Item">Improved and optimized version of LZ77 algorithm</TD></TR>
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70 <TR> <TD class="Item">PPMD</TD> <TD class="Item">Dmitry Shkarin's PPMdH with small changes</TD></TR>
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71 <TR> <TD class="Item">BCJ</TD> <TD class="Item">Converter for 32-bit x86 executables</TD></TR>
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72 <TR> <TD class="Item">BCJ2</TD> <TD class="Item">Converter for 32-bit x86 executables</TD></TR>
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73 <TR> <TD class="Item">BZip2</TD> <TD class="Item">Standard BWT algorithm</TD></TR>
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74 <TR> <TD class="Item">Deflate</TD> <TD class="Item">Standard LZ77-based algorithm</TD></TR>
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77 <P><B>LZMA</B> is default and general compression method of <B>7z</B> format. The main features of <B>LZMA</B> method:</P>
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79 <LI>High compression ratio
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80 <LI>Variable dictionary size (up to 4 GB)
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81 <LI>Compressing speed: about 1 MB/s on 2 GHz CPU
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82 <LI>Decompressing speed: about 10-20 MB/s on 2 GHz CPU
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83 <LI>Small memory requirements for decompressing (depend from dictionary size)
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84 <LI>Small code size for decompressing: about 5 KB
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85 <LI>Supporting multi-threading and P4's hyper-threading
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88 <P><B>LZMA</B> compression algorithm is very suitable for embedded applications.
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89 <B>LZMA</B> is released under the terms of the GNU LGPL. <B>LZMA</B> is also
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90 available under a proprietary license for those who can not use the GNU LGPL in
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91 their code. If you want to use <B>LZMA</B> code, you can ask consultations,
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92 custom code programming and required developer licenses
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93 from page for support:
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94 <A href="support.html">Send message to LZMA developer</A>.
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95 Check also information about <A href ="sdk.html">LZMA SDK</A>.</P>
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97 <P>7-Zip also supports encryption with AES-256 algorithm.
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98 This algorithm uses cipher key with length of 256 bits. To create that key 7-Zip
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99 uses derivation function based on SHA-256 hash algorithm.
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100 A key derivation function produces a derived key from text password defined by user.
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101 For increasing the cost of exhaustive search for passwords 7-Zip uses big number
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102 of iterations to produce cipher key from text password.</P>
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104 <P><B>7z</B> is a part of <A href="./">7-Zip</A> program distributed under the GNU LGPL.
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105 You can download <B>7-Zip</B> sources and binaries from <A href ="download.html">Download Page</A>.</P>
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107 <p>Applications that support <B>7z</B> archives: WinRAR, PowerArchiver, TUGZip, IZArc.</p>
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111 <li><A href="http://en.wikipedia.org/wiki/7z">7z at Wikipedia</A></li>
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114 <HR><P><SMALL>Copyright (C) 2009 Igor Pavlov.</SMALL></P>
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