NAME

       ccguess - search for ccrypt encryption keys

SYNOPSIS

       ccguess [options] file...

DESCRIPTION

       The  ccguess program attempts to guess ccrypt(1) encryption keys by searching the relevant
       part of the key space. This is done by prompting the user for an approximate key and  then
       trying  many variations of this key. This is intended to assist ccrypt users in recovering
       mistyped or forgotten keys, provided that they remember at least part of the key.

       Note that ccrypt provides strong cryptographic security: there are no special  back  doors
       or  shortcuts  to  recovering forgotten keys. Therefore, the ccguess program does not have
       any special powers. It simply works by trying different keys until  a  possible  match  is
       found.

       A  search  of  the  entire key space is not usually a practical option.  ccguess therefore
       works by prompting the user for an approximate key. It then tries all variations that  can
       be  obtained by applying a small number of changes. Here, each change is either a deletion
       of one letter, an insertion of one letter, a replacement of one letter by  another,  or  a
       transposition  of  two adjacent letters. By default, ccguess searches all keys that differ
       from the approximate key by up to 5  changes.  The  number  of  changes  searched  can  be
       adjusted with the --depth option.

       The  mechanism by which ccguess determines whether a key is a "possible match" is the same
       as that used by ccrypt to reject non-matching decryption keys. There is a small chance  of
       a  false  match, i.e., ccguess may find a key that turns out not to be the true encryption
       key and does not decrypt the file correctly. A false match happens approximately once  for
       every  4.3  billion  keywords  tried,  so  the  longer your search goes on, the higher the
       likelihood that a false match is found. Normally, ccguess stops after the  first  possible
       match  is  found,  but  the  -c  option  can  be  used  to search for additional keys. The
       possibility of a false match can be further reduced by supplying multiple files that  have
       been  encrypted  with  the same key. In this case, ccguess will search for keys that match
       any of the files, but will print a warning for keys that do not match all of the files.

OPTIONS

       The following options are supported:

       -h, --help
                 Help. Print usage information and exit.

       -L, --license
                 Print license info and exit.

       -V, --version
                 Print version info and exit.

       -K key, --key key
                 Specify the approximate key on the command line, rather than prompting the  user
                 for it.

       -d n, --depth n
                 Search keys that contain up to n changes. The default is 5.

       -c, --continue
                 Keep  trying  more keys even after the first match is found. By default, ccguess
                 will stop after the first key is found that matches all input files.

       -t chars, --chartable chars
                 Specify the list of characters  to  try  for  replacements  and  insertions.  By
                 default,  ccguess  will  try  all  printable  ASCII characters. If you know, for
                 example, that your key only used lowercase letters and numbers, you can speed up
                 the  search  by  specifying  a  list  of  characters  explicitly. This option is
                 mutually exclusive with -n.

       -n, --non-printable
                 Allow non-printable characters in  keys.  By  default,  ccguess  will  only  try
                 printable  ASCII  characters.  Note  that  the use of this option slows down the
                 search significantly. This option is mutually exclusive with -t.

ARGUMENTS

       file      The name of a file that has been encrypted with the unknown key.  This  file  is
                 only  read  from,  not  written  to.  The special filename "-" is used to denote
                 standard input.

                 If multiple files are specified, ccguess will search for keys that match any  of
                 the files, but will print a warning for keys that do not match all of the files.

EXAMPLE

       Suppose  the  file  myfile.cpt has been encrypted with the key "gardenhouse", but the user
       remembers "gardenhose". The command

          ccguess -K gardenhose myfile.cpt

       will find the correct key after 2318 guesses.

EXIT STATUS

       The exit status is 0 if at least one possible match is found, 1 if no matches  are  found,
       and >=2 if an error occurred.

VERSION

       1.11

AUTHOR

       Peter Selinger <selinger at users.sourceforge.net>

COPYRIGHT

       Copyright (C) 2000-2018 Peter Selinger

       This program is free software; you can redistribute it and/or modify it under the terms of
       the GNU General Public License as  published  by  the  Free  Software  Foundation;  either
       version 2 of the License, or (at your option) any later version.

       This  program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
       without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR  PURPOSE.
       See the GNU General Public License for more details.

       You should have received a copy of the GNU General Public License along with this program;
       if not, write to the Free Software Foundation, Inc.,  51  Franklin  Street,  Fifth  Floor,
       Boston, MA 02110-1301, USA.  See also http://www.gnu.org/.