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/cvs/fcrackzip/fcrackzip.txt
Revision: 1.1
Committed: Mon Aug 4 07:09:51 2008 UTC (16 years, 3 months ago) by root
Content type: text/plain
Branch: MAIN
CVS Tags: HEAD
Log Message:
initial check-in, also 1.0 check-in

File Contents

# Content
1 FCRACKZIP(1) FCRACKZIP(1)
2
3
4
5 NNAAMMEE
6 _f_c_r_a_c_k_z_i_p - a Free/Fast Zip Password Cracker
7
8 SSYYNNOOPPSSIISS
9 ffccrraacckkzziipp [-bDBchVvplum2] [--brute-force] [--dictionary] [--benchmark]
10 [--charset characterset] [--help] [--validate] [--verbose] [--init-
11 password string/path] [--length min-max] [--use-unzip] [--method name]
12 [--modulo r/m] file...
13
14 DDEESSCCRRIIPPTTIIOONN
15 _f_c_r_a_c_k_z_i_p searches each zipfile given for encrypted files and tries to
16 guess the password. All files must be encrypted with the same password,
17 the more files you provide, the better.
18
19 OOPPTTIIOONNSS
20 --hh,, ----hheellpp
21 Prints the version number and (hopefully) some helpful insights.
22
23 --vv,, ----vveerrbboossee
24 Each -v makes the program more verbose.
25
26 --bb,, ----bbrruuttee--ffoorrccee
27 Select brute force mode. This tries all possible combinations of
28 the letters you specify.
29
30 --DD,, ----ddiiccttiioonnaarryy
31 Select dictionary mode. In this mode, fcrackzip will read pass-
32 words from a file, which must contain one password per line and
33 should be alphabetically sorted (e.g. using ssoorrtt((11))).
34
35 --cc,, ----cchhaarrsseett cchhaarraacctteerrsseett--ssppeecciiffiiccaattiioonn
36 Select the characters to use in brute-force cracking. Must be
37 one of
38
39 a include all lowercase characters [a-z]
40 A include all uppercase characters [A-Z]
41 1 include the digits [0-9]
42 ! include [!:$%&/()=?{[]}+*~#]
43 : the following characters upto the end of the spe-
44 cification string are included in the character set.
45 This way you can include any character except binary
46 null (at least under unix).
47
48 For example, a1:$% selects lowercase characters, digits and the
49 dollar and percent signs.
50
51 --pp,, ----iinniitt--ppaasssswwoorrdd ssttrriinngg
52 Set initial (starting) password for brute-force searching to
53 _s_t_r_i_n_g, or use the file with the name _s_t_r_i_n_g to supply passwords
54 for dictionary searching.
55
56 --ll,, ----lleennggtthh mmiinn[[--mmaaxx]]
57 Use an initial password of length min, and check all passwords
58 upto passwords of length max (including). You can omit the max
59 parameter.
60
61 --uu,, ----uussee--uunnzziipp
62 Try to decompress the first file by calling unzip with the
63 guessed password. This weeds out false positives when not enough
64 files have been given.
65
66 --mm,, ----mmeetthhoodd nnaammee
67 Use method number "name" instead of the default cracking method.
68 The switch ----hheellpp will print a list of available methods. Use
69 ----bbeenncchhmmaarrkk to see which method does perform best on your
70 machine. The nnaammee can also be the number of the method to use.
71
72 --22,, ----mmoodduulloo rr//mm
73 Calculate only r/m of the password. Not yet supported.
74
75 --BB,, ----bbeenncchhmmaarrkk
76 Make a small benchmark, the output is nearly meaningless.
77
78 --VV,, ----vvaalliiddaattee
79 Make some basic checks wether the cracker works.
80
81 ZZIIPP PPAASSSSWWOORRDD BBAASSIICCSS
82 Have you ever mis-typed a password for unzip? Unzip reacted pretty fast
83 with ´incorrect password´, _w_i_t_h_o_u_t decrypting the whole file. While the
84 encryption algorithm used by zip is relatively secure, PK made cracking
85 easy by providing hooks for very fast password-checking, directly in
86 the zip file. Understanding these is crucial to zip password cracking:
87
88 For each password that is tried, the first twelve bytes of the file are
89 decrypted. Depending on the version of zip used to encrypt the file
90 (more on that later), the first ten or eleven bytes are random, fol-
91 lowed by one or two bytes whose values are stored elsewhere in the zip
92 file, i.e. are known beforehand. If these last bytes don't have the
93 correct (known) value, the password is definitely wrong. If the bytes
94 are correct, the password _m_i_g_h_t be correct, but the only method to find
95 out is to unzip the file and compare the uncompressed length and crc´s.
96
97 Earlier versions of pkzip (1.xx) (and, incidentally, many zip clones
98 for other operating systems!) stored two known bytes. Thus the error
99 rate was roughly 1/2^16 = 0.01%. PKWARE ´improved´ (interesting what
100 industry calls improved) the security of their format by only including
101 one byte, so the possibility of false passwords is now raised to 0.4%.
102 Unfortunately, there is no real way to distinguish one byte from two
103 byte formats, so we have to be conservative.
104
105 BBRRUUTTEE FFOORRCCEE MMOODDEE
106 By default, brute force starts at the given starting password, and suc-
107 cessively tries all combinations until they are exhausted, printing all
108 passwords that it detects, together with a rough correctness indicator.
109
110 The starting password given by the _-_p switch determines the length.
111 fcrackzip will not currently increase the password length automati-
112 cally, unless the _-_l switch is used.
113
114 DDIICCTTIIOONNAARRYY MMOODDEE
115 This mode is similar to brute force mode, but instead of generating
116 passwords using a given set of characters and a length, the passwords
117 will be read from a file that you have to specify using the _-_p switch.
118
119 CCPP MMAASSKK
120 A CP mask is a method to obscure images or parts of images using a
121 password. These obscured images can be restored even when saved as
122 JPEG files. In most of these files the password is actually hidden and
123 can be decoded easily (using one of the many available viewer and mask-
124 ing programs, e.g. xv). If you convert the image the password, however,
125 is lost. The ccppmmaasskk crack method can be used to brute-force these
126 images. Instead of a zip file you supply the obscured part (and nothing
127 else) of the image in the PPPPMM-Image Format (xxvv and other viewers can
128 easily do this).
129
130 The ccppmmaasskk method can only cope with password composed of uppercase
131 letters, so be sure to supply the ----cchhaarrsseett AA or equivalent option,
132 together with a suitable initialization password.
133
134 EEXXAAMMPPLLEESS
135 ffccrraacckkzziipp --cc aa --pp aaaaaaaaaaaa ssaammppllee..zziipp
136 checks the encrypted files in sample.zip for all lowercase 6
137 character passwords (aaaaaa ... abaaba ... ghfgrg ... zzzzzz).
138
139 ffccrraacckkzziipp ----mmeetthhoodd ccppmmaasskk ----cchhaarrsseett AA ----iinniitt AAAAAAAA tteesstt..ppppmm
140 checks the obscured image tteesstt..ppppmm for all four character pass-
141 words. -TP ffccrraacckkzziipp --DD --pp ppaasssswwoorrddss..ttxxtt ssaammppllee..zziipp check for
142 every password listed in the file ppaasssswwoorrddss..ttxxtt.
143
144 PPEERRFFOORRMMAANNCCEE
145 _f_z_c, which seems to be widely used as a fast password cracker, claims
146 to make 204570 checks per second on my machine (measured under plain
147 dos w/o memory manager).
148
149 _f_c_r_a_c_k_z_i_p, being written in C and not in assembler, naturally is
150 slower. Measured on a slightly loaded unix (same machine), it´s 12 per-
151 cent slower (the compiler used was _p_g_c_c, from hhttttpp::////wwwwww..ggcccc..mmll..oorrgg//).
152
153 To remedy this a bit, I converted small parts of the encryption core to
154 x86 assembler (it will still compile on non x86 machines), and now it´s
155 about 4-12 percent faster than _f_z_c (again, the _f_c_r_a_c_k_z_i_p performance
156 was measured under a multitasking os, so there are inevitably some
157 meaurement errors), so there shouldn't be a tempting reason to switch
158 to other programs.
159
160 Further improvements are definitely possible: _f_z_c took 4 years to get
161 into shape, while fcrackzip was hacked together in under 10 hours. And
162 not to forget you have the source, while other programs (like _f_z_c),
163 even come as an _e_n_c_r_y_p_t_e_d _._e_x_e file (maybe because their programmers
164 are afraid of other people could having a look at their lack of pro-
165 gramming skills? nobody knows...)
166
167 RRAATTIIOONNAALLEE
168 The reason I wrote _f_c_r_a_c_k_z_i_p was NNOOTT to have the fastest zip cracker
169 available, but to provide a _p_o_r_t_a_b_l_e, _f_r_e_e (thus _e_x_t_e_n_s_i_b_l_e), but still
170 _f_a_s_t zip password cracker. I was really pissed of with that dumb,
171 nonextendable zipcrackers that were either slow, were too limited, or
172 wouldn't run in the background (say, under unix). (And you can't run
173 them on your superfast 600Mhz Alpha).
174
175 BBUUGGSS
176 No automatic unzip checking.
177
178 Stop/resume facility is missing.
179
180 Should be able to distinguish between files with 16 bit stored CRC´s
181 and 8 bit stored CRC´s.
182
183 The benchmark does not work on all systems.
184
185 It's still early alpha.
186
187 Method "cpmask" only accepts ppms.
188
189 Could be faster.
190
191 AAUUTTHHOORR
192 _f_c_r_a_c_k_z_i_p was written by Marc Lehmann <pcg@goof.com>. The main
193 _f_c_r_a_c_k_z_i_p page is at hhttttpp::////wwwwww..ggooooff..ccoomm//ppccgg//mmaarrcc//ffccrraacckkzziipp..hhttmmll)
194
195
196
197
198 Free/Fast Zip Password Cracker FCRACKZIP(1)