Provided by: fcrackzip_0.3-2_i386 bug

NAME

       fcrackzip - a Free/Fast Zip Password Cracker

SYNOPSIS

       fcrackzip  [-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...

DESCRIPTION

       fcrackzip searches each zipfile given for encrypted files and tries  to
       guess the password. All files must be encrypted with the same password,
       the more files you provide, the better.

   OPTIONS
       -h, --help
              Prints the version number and (hopefully) some helpful insights.

       -v, --verbose
              Each -v makes the program more verbose.

       -b, --brute-force
              Select brute force mode. This tries all possible combinations of
              the letters you specify.

       -D, --dictionary
              Select dictionary  mode.  In  this  mode,  fcrackzip  will  read
              passwords  from a file, which must contain one password per line
              and should be alphabetically sorted (e.g. using sort(1)).

       -c, --charset characterset-specification
              Select the characters to use in brute-force  cracking.  Must  be
              one of

                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).

              For  example, a1:$% selects lowercase characters, digits and the
              dollar and percent signs.

       -p, --init-password string
              Set initial (starting) password  for  brute-force  searching  to
              string, or use the file with the name string to supply passwords
              for dictionary searching.

       -l, --length min[-max]
              Use an initial password of length min, and check  all  passwords
              upto  passwords  of length max (including). You can omit the max
              parameter.

       -u, --use-unzip
              Try to decompress the first  file  by  calling  unzip  with  the
              guessed password. This weeds out false positives when not enough
              files have been given.

       -m, --method name
              Use method number "name" instead of the default cracking method.
              The  switch  --help  will print a list of available methods. Use
              --benchmark to see  which  method  does  perform  best  on  your
              machine. The name can also be the number of the method to use.

       -2, --modulo r/m
              Calculate only r/m of the password. Not yet supported.

       -B, --benchmark
              Make a small benchmark, the output is nearly meaningless.

       -V, --validate
              Make some basic checks wether the cracker works.

ZIP PASSWORD BASICS

       Have you ever mis-typed a password for unzip? Unzip reacted pretty fast
       with ´incorrect password´, without decrypting the whole file. While the
       encryption algorithm used by zip is relatively secure, PK made cracking
       easy by providing hooks for very fast  password-checking,  directly  in
       the zip file. Understanding these is crucial to zip password cracking:

       For each password that is tried, the first twelve bytes of the file are
       decrypted. Depending on the version of zip used  to  encrypt  the  file
       (more  on  that  later),  the  first  ten  or  eleven bytes are random,
       followed by one or two bytes whose values are stored elsewhere  in  the
       zip file, i.e. are known beforehand. If these last bytes don’t have the
       correct (known) value, the password is definitely wrong. If  the  bytes
       are correct, the password might be correct, but the only method to find
       out is to unzip the file and compare the uncompressed length and crc´s.

       Earlier  versions  of  pkzip (1.xx) (and, incidentally, many zip clones
       for other operating systems!) stored two known bytes.  Thus  the  error
       rate  was  roughly  1/2^16 = 0.01%. PKWARE ´improved´ (interesting what
       industry calls improved) the security of their format by only including
       one  byte, so the possibility of false passwords is now raised to 0.4%.
       Unfortunately, there is no real way to distinguish one  byte  from  two
       byte formats, so we have to be conservative.

BRUTE FORCE MODE

       By  default,  brute  force  starts  at the given starting password, and
       successively tries all combinations until they are exhausted,  printing
       all  passwords  that  it  detects,  together  with  a rough correctness
       indicator.

       The starting password given by the -p  switch  determines  the  length.
       fcrackzip   will   not   currently   increase   the   password   length
       automatically, unless the -l switch is used.

DICTIONARY MODE

       This mode is similar to brute force mode,  but  instead  of  generating
       passwords  using  a given set of characters and a length, the passwords
       will be read from a file that you have to specify using the -p  switch.

CP MASK

       A  CP  mask  is  a  method to obscure images or parts of images using a
       password.  These obscured images can be restored  even  when  saved  as
       JPEG  files. In most of these files the password is actually hidden and
       can be decoded easily (using one  of  the  many  available  viewer  and
       masking  programs,  e.g.  xv).  If  you convert the image the password,
       however, is lost. The cpmask crack method can be  used  to  brute-force
       these  images.  Instead of a zip file you supply the obscured part (and
       nothing else) of the image  in  the  PPM-Image  Format  (xv  and  other
       viewers can easily do this).

       The  cpmask  method  can  only cope with password composed of uppercase
       letters, so be sure to supply the --charset  A  or  equivalent  option,
       together with a suitable initialization password.

EXAMPLES

       fcrackzip -c a -p aaaaaa sample.zip
              checks  the  encrypted  files  in sample.zip for all lowercase 6
              character passwords (aaaaaa ... abaaba ... ghfgrg ... zzzzzz).

       fcrackzip --method cpmask --charset A --init AAAA test.ppm
              checks the  obscured  image  test.ppm  for  all  four  character
              passwords.   -TP  fcrackzip -D -p passwords.txt sample.zip check
              for every password listed in the file passwords.txt.

PERFORMANCE

       fzc, which seems to be widely used as a fast password  cracker,  claims
       to  make  204570  checks per second on my machine (measured under plain
       dos w/o memory manager).

       fcrackzip, being written in  C  and  not  in  assembler,  naturally  is
       slower.  Measured  on  a  slightly  loaded unix (same machine), it´s 12
       percent    slower    (the    compiler    used    was     pgcc,     from
       http://www.gcc.ml.org/).

       To remedy this a bit, I converted small parts of the encryption core to
       x86 assembler (it will still compile on non x86 machines), and now it´s
       about  4-12  percent  faster than fzc (again, the fcrackzip performance
       was measured under a multitasking os,  so  there  are  inevitably  some
       meaurement  errors),  so there shouldn’t be a tempting reason to switch
       to other programs.

       Further improvements are definitely possible: fzc took 4 years  to  get
       into  shape, while fcrackzip was hacked together in under 10 hours. And
       not to forget you have the source, while  other  programs  (like  fzc),
       even  come  as  an encrypted .exe file (maybe because their programmers
       are afraid of other people  could  having  a  look  at  their  lack  of
       programming skills?  nobody knows...)

RATIONALE

       The  reason  I  wrote fcrackzip was NOT to have the fastest zip cracker
       available, but to provide a portable, free (thus extensible), but still
       fast  zip  password  cracker.  I  was  really pissed of with that dumb,
       nonextendable zipcrackers that were either slow, were too  limited,  or
       wouldn’t  run  in  the background (say, under unix). (And you can’t run
       them on your superfast 600Mhz Alpha).

BUGS

       No automatic unzip checking.

       Stop/resume facility is missing.

       Should be able to distinguish between files with 16  bit  stored  CRC´s
       and 8 bit stored CRC´s.

       The benchmark does not work on all systems.

       It’s still early alpha.

       Method "cpmask" only accepts ppms.

       Could be faster.

AUTHOR

       fcrackzip   was  written  by  Marc  Lehmann  <pcg@goof.com>.  The  main
       fcrackzip page is at http://www.goof.com/pcg/marc/fcrackzip.html)

                        Free/Fast Zip Password Cracker            FCRACKZIP(1)