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<HTML><HEAD><TITLE>Manpage of FCRACKZIP</TITLE></HEAD><BODY><H1>FCRACKZIP</H1>Section: User Commands (1)<BR>Updated: Free/Fast Zip Password Cracker<BR><A HREF="#index">Index</A><HR><A NAME="lbAB"> </A><H2>NAME</H2><I>fcrackzip</I>- a Free/Fast Zip Password Cracker<A NAME="lbAC"> </A><H2>SYNOPSIS</H2><B>fcrackzip</B>[-bDBchVvplum2] [--brute-force] [--dictionary] [--benchmark] [--charset characterset][--help] [--validate] [--verbose] [--init-password string/path] [--length min-max][--use-unzip] [--method name] [--modulo r/m] file...<A NAME="lbAD"> </A><H2>DESCRIPTION</H2><I>fcrackzip</I>searches each zipfile given for encrypted files and tries to guess thepassword. All files must be encrypted with the same password, the morefiles you provide, the better.<A NAME="lbAE"> </A><H3>OPTIONS</H3><DL COMPACT><DT><B>-h, --help</B><DD>Prints the version number and (hopefully) some helpful insights.<DT><B>-v, --verbose</B><DD>Each -v makes the program more verbose.<DT><B>-b, --brute-force</B><DD>Select brute force mode. This tries all possible combinationsof the letters you specify.<DT><B>-D, --dictionary</B><DD>Select dictionary mode. In this mode, fcrackzip will read passwordsfrom a file, which must contain one password per line and should bealphabetically sorted (e.g. using <B>(1)</B>).<DT><B>-c, --charset characterset-specification</B><DD>Select the characters to use in brute-force cracking. Must be oneof<P><PRE> a include all lowercase characters [a-z] A include all uppercase characters [A-Z] 1 include the digits [0-9] ! include [!:$%&/()=?{[]}+*~#] : the following characters upto the end of the spe- cification string are included in the character set. This way you can include any character except binary null (at least under unix).</PRE><P>For example, a1:$% selects lowercase characters, digits and the dollar andpercent signs.<DT><B>-p, --init-password string</B><DD>Set initial (starting) password for brute-force searching to <I>string</I>,or use the file with the name <I>string</I> to supply passwords for dictionarysearching.<DT><B>-l, --length min[-max]</B><DD>Use an initial password of length min, and check all passwordsupto passwords of length max (including). You can omit the maxparameter.<DT><B>-u, --use-unzip</B><DD>Try to decompress the first file by calling unzip with the guessedpassword. This weeds out false positives when not enough files havebeen given.<DT><B>-m, --method name</B><DD>Use method number "name" instead of the default cracking method. Theswitch <B>--help</B> will print a list of available methods. Use<B>--benchmark</B> to see which method does perform best on yourmachine. The <B>name</B> can also be the number of the method to use.<DT><B>-2, --modulo r/m</B><DD>Calculate only r/m of the password. Not yet supported.<DT><B>-B, --benchmark</B><DD>Make a small benchmark, the output is nearly meaningless.<DT><B>-V, --validate</B><DD>Make some basic checks wether the cracker works.</DL><A NAME="lbAF"> </A><H2>ZIP PASSWORD BASICS</H2>Have you ever mis-typed a password for unzip? Unzip reacted pretty fast with'incorrect password', <I>without</I> decrypting the whole file. While theencryption algorithm used by zip is relatively secure, PK made cracking easyby providing hooks for very fast password-checking, directly in the zipfile. Understanding these is crucial to zip password cracking:<P>For each password that is tried, the first twelve bytes of the file aredecrypted. Depending on the version of zip used to encrypt the file (more onthat later), the first ten or eleven bytes are random, followed by one ortwo bytes whose values are stored elsewhere in the zip file, i.e. are knownbeforehand. If these last bytes don't have the correct (known) value, thepassword is definitely wrong. If the bytes are correct, the password<I>might</I> be correct, but the only method to find out is to unzip the fileand compare the uncompressed length and crc's.<P>Earlier versions of pkzip (1.xx) (and, incidentally, many zip clones forother operating systems!) stored two known bytes. Thus the error rate wasroughly 1/2^16 = 0.01%. PKWARE 'improved' (interesting what industry callsimproved) the security of their format by only including one byte, so thepossibility of false passwords is now raised to 0.4%. Unfortunately, thereis no real way to distinguish one byte from two byte formats, so we have tobe conservative.<A NAME="lbAG"> </A><H2>BRUTE FORCE MODE</H2>By default, brute force starts at the given starting password, andsuccessively tries all combinations until they are exhausted, printing allpasswords that it detects, together with a rough correctness indicator.<P>The starting password given by the <I>-p</I> switch determines the length.fcrackzip will not currently increase the password length automatically, unlessthe <I>-l</I> switch is used.<A NAME="lbAH"> </A><H2>DICTIONARY MODE</H2>This mode is similar to brute force mode, but instead of generating passwordsusing a given set of characters and a length, the passwords will be read froma file that you have to specify using the <I>-p</I> switch.<A NAME="lbAI"> </A><H2>CP MASK</H2>A CP mask is a method to obscure images or parts of images using apassword. These obscured images can be restored even when saved as JPEGfiles. In most of these files the password is actually hidden and canbe decoded easily (using one of the many available viewer and maskingprograms, e.g. xv). If you convert the image the password, however, islost. The <B>cpmask</B> crack method can be used to brute-force theseimages. Instead of a zip file you supply the obscured part (and nothingelse) of the image in the <B>PPM</B>-Image Format (<B>xv</B> and otherviewers can easily do this).<P>The <B>cpmask</B> method can only cope with password composed of uppercaseletters, so be sure to supply the <B>--charset A</B> or equivalent option,together with a suitable initialization password.<A NAME="lbAJ"> </A><H2>EXAMPLES</H2><DL COMPACT><DT><B>fcrackzip -c a -p aaaaaa sample.zip</B><DD>checks the encrypted files in sample.zip for all lowercase 6 characterpasswords (aaaaaa ... abaaba ... ghfgrg ... zzzzzz).<DT><B>fcrackzip --method cpmask --charset A --init AAAA test.ppm</B><DD>checks the obscured image <B>test.ppm</B> for all four character passwords.-TP<B>fcrackzip -D -p passwords.txt sample.zip</B>check for every password listed in the file <B>passwords.txt</B>.</DL><A NAME="lbAK"> </A><H2>PERFORMANCE</H2><I>fzc</I>, which seems to be widely used as a fast password cracker,claims to make 204570 checks per second on my machine (measured under plaindos w/o memory manager).<P><I>fcrackzip</I>, being written in C and not in assembler, naturallyis slower. Measured on a slightly loaded unix (same machine), it's 12percent slower (the compiler used was <I>pgcc</I>, from<B><A HREF="http://www.gcc.ml.org/">http://www.gcc.ml.org/</A></B>).<P>To remedy this a bit, I converted small parts of the encryption core to x86assembler (it will still compile on non x86 machines), and now it's about4-12 percent faster than <I>fzc</I> (again, the <I>fcrackzip</I> performancewas measured under a multitasking os, so there are inevitably somemeaurement errors), so there shouldn't be a tempting reason to switch toother programs.<P>Further improvements are definitely possible: <I>fzc</I> took 4 years to getinto shape, while fcrackzip was hacked together in under 10 hours. And not toforget you have the source, while other programs (like <I>fzc</I>), even comeas an <I>encrypted .exe</I> file (maybe because their programmers are afraidof other people could having a look at their lack of programming skills?nobody knows...)<A NAME="lbAL"> </A><H2>RATIONALE</H2>The reason I wrote <I>fcrackzip</I> was <B>NOT</B> to have the fastest zipcracker available, but to provide a <I>portable</I>, <I>free</I> (thus<I>extensible</I>), but still <I>fast</I> zip password cracker. I was reallypissed of with that dumb, nonextendable zipcrackers that were either slow,were too limited, or wouldn't run in the background (say, under unix). (Andyou can't run them on your superfast 600Mhz Alpha).<A NAME="lbAM"> </A><H2>BUGS</H2>No automatic unzip checking.<P>Stop/resume facility is missing.<P>Should be able to distinguish between files with 16 bit stored CRC's and 8bit stored CRC's.<P>The benchmark does not work on all systems.<P>It's still early alpha.<P>Method "cpmask" only accepts ppms.<P>Could be faster.<A NAME="lbAN"> </A><H2>AUTHOR</H2><I>fcrackzip</I> was written by Marc Lehmann <<A HREF="mailto:pcg@goof.com">pcg@goof.com</A>>. The main<I>fcrackzip</I> page is at <B><A HREF="http://www.goof.com/pcg/marc/fcrackzip.html">http://www.goof.com/pcg/marc/fcrackzip.html</A></B>)<P><P><HR><A NAME="index"> </A><H2>Index</H2><DL><DT><A HREF="#lbAB">NAME</A><DD><DT><A HREF="#lbAC">SYNOPSIS</A><DD><DT><A HREF="#lbAD">DESCRIPTION</A><DD><DL><DT><A HREF="#lbAE">OPTIONS</A><DD></DL><DT><A HREF="#lbAF">ZIP PASSWORD BASICS</A><DD><DT><A HREF="#lbAG">BRUTE FORCE MODE</A><DD><DT><A HREF="#lbAH">DICTIONARY MODE</A><DD><DT><A HREF="#lbAI">CP MASK</A><DD><DT><A HREF="#lbAJ">EXAMPLES</A><DD><DT><A HREF="#lbAK">PERFORMANCE</A><DD><DT><A HREF="#lbAL">RATIONALE</A><DD><DT><A HREF="#lbAM">BUGS</A><DD><DT><A HREF="#lbAN">AUTHOR</A><DD></DL><HR>This document was created by,using the manual pages.<BR>Time: 23:52:36 GMT, June 18, 2000</BODY></HTML>?? 快捷鍵說明
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