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Revision: 1.1
Committed: Mon Aug 4 07:09:50 2008 UTC (16 years, 3 months ago) by root
Content type: text/html
Branch: MAIN
CVS Tags: HEAD
Log Message:
initial check-in, also 1.0 check-in

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# Content
1 <HTML><HEAD><TITLE>Manpage of FCRACKZIP</TITLE>
2 </HEAD><BODY>
3 <H1>FCRACKZIP</H1>
4 Section: User Commands (1)<BR>Updated: Free/Fast Zip Password Cracker<BR><A HREF="#index">Index</A>
5 <HR>
6
7 <A NAME="lbAB">&nbsp;</A>
8 <H2>NAME</H2>
9
10 <I>fcrackzip</I>
11
12 - a Free/Fast Zip Password Cracker
13 <A NAME="lbAC">&nbsp;</A>
14 <H2>SYNOPSIS</H2>
15
16 <B>fcrackzip</B>
17
18 [-bDBchVvplum2] [--brute-force] [--dictionary] [--benchmark] [--charset characterset]
19 [--help] [--validate] [--verbose] [--init-password string/path] [--length min-max]
20 [--use-unzip] [--method name] [--modulo r/m] file...
21 <A NAME="lbAD">&nbsp;</A>
22 <H2>DESCRIPTION</H2>
23
24 <I>fcrackzip</I>
25
26 searches each zipfile given for encrypted files and tries to guess the
27 password. All files must be encrypted with the same password, the more
28 files you provide, the better.
29 <A NAME="lbAE">&nbsp;</A>
30 <H3>OPTIONS</H3>
31
32 <DL COMPACT>
33 <DT><B>-h, --help</B>
34
35 <DD>
36 Prints the version number and (hopefully) some helpful insights.
37 <DT><B>-v, --verbose</B>
38
39 <DD>
40 Each -v makes the program more verbose.
41 <DT><B>-b, --brute-force</B>
42
43 <DD>
44 Select brute force mode. This tries all possible combinations
45 of the letters you specify.
46 <DT><B>-D, --dictionary</B>
47
48 <DD>
49 Select dictionary mode. In this mode, fcrackzip will read passwords
50 from a file, which must contain one password per line and should be
51 alphabetically sorted (e.g. using <B>(1)</B>).
52 <DT><B>-c, --charset characterset-specification</B>
53
54 <DD>
55 Select the characters to use in brute-force cracking. Must be one
56 of
57 <P>
58 <PRE>
59 a include all lowercase characters [a-z]
60 A include all uppercase characters [A-Z]
61 1 include the digits [0-9]
62 ! include [!:$%&amp;/()=?{[]}+*~#]
63 : the following characters upto the end of the spe-
64 cification string are included in the character set.
65 This way you can include any character except binary
66 null (at least under unix).
67 </PRE>
68
69 <P>
70 For example, a1:$% selects lowercase characters, digits and the dollar and
71 percent signs.
72 <DT><B>-p, --init-password string</B>
73
74 <DD>
75 Set initial (starting) password for brute-force searching to <I>string</I>,
76 or use the file with the name <I>string</I> to supply passwords for dictionary
77 searching.
78 <DT><B>-l, --length min[-max]</B>
79
80 <DD>
81 Use an initial password of length min, and check all passwords
82 upto passwords of length max (including). You can omit the max
83 parameter.
84 <DT><B>-u, --use-unzip</B>
85
86 <DD>
87 Try to decompress the first file by calling unzip with the guessed
88 password. This weeds out false positives when not enough files have
89 been given.
90 <DT><B>-m, --method name</B>
91
92 <DD>
93 Use method number &quot;name&quot; instead of the default cracking method. The
94 switch <B>--help</B> will print a list of available methods. Use
95 <B>--benchmark</B> to see which method does perform best on your
96 machine. The <B>name</B> can also be the number of the method to use.
97 <DT><B>-2, --modulo r/m</B>
98
99 <DD>
100 Calculate only r/m of the password. Not yet supported.
101 <DT><B>-B, --benchmark</B>
102
103 <DD>
104 Make a small benchmark, the output is nearly meaningless.
105 <DT><B>-V, --validate</B>
106
107 <DD>
108 Make some basic checks wether the cracker works.
109 </DL>
110 <A NAME="lbAF">&nbsp;</A>
111 <H2>ZIP PASSWORD BASICS</H2>
112
113 Have you ever mis-typed a password for unzip? Unzip reacted pretty fast with
114 'incorrect password', <I>without</I> decrypting the whole file. While the
115 encryption algorithm used by zip is relatively secure, PK made cracking easy
116 by providing hooks for very fast password-checking, directly in the zip
117 file. Understanding these is crucial to zip password cracking:
118 <P>
119 For each password that is tried, the first twelve bytes of the file are
120 decrypted. Depending on the version of zip used to encrypt the file (more on
121 that later), the first ten or eleven bytes are random, followed by one or
122 two bytes whose values are stored elsewhere in the zip file, i.e. are known
123 beforehand. If these last bytes don't have the correct (known) value, the
124 password is definitely wrong. If the bytes are correct, the password
125 <I>might</I> be correct, but the only method to find out is to unzip the file
126 and compare the uncompressed length and crc's.
127 <P>
128 Earlier versions of pkzip (1.xx) (and, incidentally, many zip clones for
129 other operating systems!) stored two known bytes. Thus the error rate was
130 roughly 1/2^16 = 0.01%. PKWARE 'improved' (interesting what industry calls
131 improved) the security of their format by only including one byte, so the
132 possibility of false passwords is now raised to 0.4%. Unfortunately, there
133 is no real way to distinguish one byte from two byte formats, so we have to
134 be conservative.
135 <A NAME="lbAG">&nbsp;</A>
136 <H2>BRUTE FORCE MODE</H2>
137
138 By default, brute force starts at the given starting password, and
139 successively tries all combinations until they are exhausted, printing all
140 passwords that it detects, together with a rough correctness indicator.
141 <P>
142 The starting password given by the <I>-p</I> switch determines the length.
143 fcrackzip will not currently increase the password length automatically, unless
144 the <I>-l</I> switch is used.
145 <A NAME="lbAH">&nbsp;</A>
146 <H2>DICTIONARY MODE</H2>
147
148 This mode is similar to brute force mode, but instead of generating passwords
149 using a given set of characters and a length, the passwords will be read from
150 a file that you have to specify using the <I>-p</I> switch.
151 <A NAME="lbAI">&nbsp;</A>
152 <H2>CP MASK</H2>
153
154 A CP mask is a method to obscure images or parts of images using a
155 password. These obscured images can be restored even when saved as JPEG
156 files. In most of these files the password is actually hidden and can
157 be decoded easily (using one of the many available viewer and masking
158 programs, e.g. xv). If you convert the image the password, however, is
159 lost. The <B>cpmask</B> crack method can be used to brute-force these
160 images. Instead of a zip file you supply the obscured part (and nothing
161 else) of the image in the <B>PPM</B>-Image Format (<B>xv</B> and other
162 viewers can easily do this).
163 <P>
164 The <B>cpmask</B> method can only cope with password composed of uppercase
165 letters, so be sure to supply the <B>--charset A</B> or equivalent option,
166 together with a suitable initialization password.
167 <A NAME="lbAJ">&nbsp;</A>
168 <H2>EXAMPLES</H2>
169
170 <DL COMPACT>
171 <DT><B>fcrackzip -c a -p aaaaaa sample.zip</B>
172
173 <DD>
174 checks the encrypted files in sample.zip for all lowercase 6 character
175 passwords (aaaaaa ... abaaba ... ghfgrg ... zzzzzz).
176 <DT><B>fcrackzip --method cpmask --charset A --init AAAA test.ppm</B>
177
178 <DD>
179 checks the obscured image <B>test.ppm</B> for all four character passwords.
180 -TP
181 <B>fcrackzip -D -p passwords.txt sample.zip</B>
182
183 check for every password listed in the file <B>passwords.txt</B>.
184 </DL>
185 <A NAME="lbAK">&nbsp;</A>
186 <H2>PERFORMANCE</H2>
187
188 <I>fzc</I>, which seems to be widely used as a fast password cracker,
189 claims to make 204570 checks per second on my machine (measured under plain
190 dos w/o memory manager).
191 <P>
192 <I>fcrackzip</I>, being written in C and not in assembler, naturally
193 is slower. Measured on a slightly loaded unix (same machine), it's 12
194 percent slower (the compiler used was <I>pgcc</I>, from
195 <B><A HREF="http://www.gcc.ml.org/">http://www.gcc.ml.org/</A></B>).
196 <P>
197 To remedy this a bit, I converted small parts of the encryption core to x86
198 assembler (it will still compile on non x86 machines), and now it's about
199 4-12 percent faster than <I>fzc</I> (again, the <I>fcrackzip</I> performance
200 was measured under a multitasking os, so there are inevitably some
201 meaurement errors), so there shouldn't be a tempting reason to switch to
202 other programs.
203 <P>
204 Further improvements are definitely possible: <I>fzc</I> took 4 years to get
205 into shape, while fcrackzip was hacked together in under 10 hours. And not to
206 forget you have the source, while other programs (like <I>fzc</I>), even come
207 as an <I>encrypted .exe</I> file (maybe because their programmers are afraid
208 of other people could having a look at their lack of programming skills?
209 nobody knows...)
210 <A NAME="lbAL">&nbsp;</A>
211 <H2>RATIONALE</H2>
212
213 The reason I wrote <I>fcrackzip</I> was <B>NOT</B> to have the fastest zip
214 cracker available, but to provide a <I>portable</I>, <I>free</I> (thus
215 <I>extensible</I>), but still <I>fast</I> zip password cracker. I was really
216 pissed of with that dumb, nonextendable zipcrackers that were either slow,
217 were too limited, or wouldn't run in the background (say, under unix). (And
218 you can't run them on your superfast 600Mhz Alpha).
219 <A NAME="lbAM">&nbsp;</A>
220 <H2>BUGS</H2>
221
222 No automatic unzip checking.
223 <P>
224
225 Stop/resume facility is missing.
226 <P>
227
228 Should be able to distinguish between files with 16 bit stored CRC's and 8
229 bit stored CRC's.
230 <P>
231
232 The benchmark does not work on all systems.
233 <P>
234
235 It's still early alpha.
236 <P>
237
238 Method &quot;cpmask&quot; only accepts ppms.
239 <P>
240
241 Could be faster.
242 <A NAME="lbAN">&nbsp;</A>
243 <H2>AUTHOR</H2>
244
245 <I>fcrackzip</I> was written by Marc Lehmann &lt;<A HREF="mailto:pcg@goof.com">pcg@goof.com</A>&gt;. The main
246 <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>)
247 <P>
248 <P>
249
250 <HR>
251 <A NAME="index">&nbsp;</A><H2>Index</H2>
252 <DL>
253 <DT><A HREF="#lbAB">NAME</A><DD>
254 <DT><A HREF="#lbAC">SYNOPSIS</A><DD>
255 <DT><A HREF="#lbAD">DESCRIPTION</A><DD>
256 <DL>
257 <DT><A HREF="#lbAE">OPTIONS</A><DD>
258 </DL>
259 <DT><A HREF="#lbAF">ZIP PASSWORD BASICS</A><DD>
260 <DT><A HREF="#lbAG">BRUTE FORCE MODE</A><DD>
261 <DT><A HREF="#lbAH">DICTIONARY MODE</A><DD>
262 <DT><A HREF="#lbAI">CP MASK</A><DD>
263 <DT><A HREF="#lbAJ">EXAMPLES</A><DD>
264 <DT><A HREF="#lbAK">PERFORMANCE</A><DD>
265 <DT><A HREF="#lbAL">RATIONALE</A><DD>
266 <DT><A HREF="#lbAM">BUGS</A><DD>
267 <DT><A HREF="#lbAN">AUTHOR</A><DD>
268 </DL>
269 <HR>
270 This document was created by
271 ,
272 using the manual pages.<BR>
273 Time: 09:44:43 GMT, February 09, 2003
274 </BODY>
275 </HTML>