--- name: "ccguess" section: "1" platform: "linux" package: "ccrypt" version: "1.11-5" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/ccguess" --- # ccguess(1) search for ccrypt encryption keys ## NAME ccguess - search for ccrypt encryption keys ## SYNOPSIS ``` ccguess [options] file... ``` ## DESCRIPTION The **ccguess** program attempts to guess [**ccrypt**(1)](/ccrypt/1.md) 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 \ ## 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/.