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/.

Version 1.11                                        July 2018                                         CCGUESS(1)