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ccrypt
Secure encryption and decryption of files and streams
_________________________________________________________________
Description
ccrypt is a tool for encrypting and decrypting files and streams.
It is based on the Rijndael block cipher, a version of which is
also used in the Advanced Encryption Standard (AES, see
http://www.nist.gov/aes). This cipher is believed to provide very
strong cryptographic security.
The algorithm provided by ccrypt is not symmetric, i.e., one must
specify whether to encrypt or decrypt. The most common way to
invoke ccrypt is via the commands ccencrypt and ccdecrypt. There
is also a ccat command for decrypting a file directly to the
terminal, thus reducing the likelihood of leaving temporary
plaintext files around. In addition, there is a compatibility mode
for decrypting legacy files from the ancient Unix crypt(1) command.
An emacs mode is also supplied for editing encrypted text files.
Encryption and decryption depends on a keyword (or key phrase)
supplied by the user. By default, the user is prompted to enter a
keyword from the terminal. Keywords can consist of any number of
characters, and all characters are significant (although ccrypt
internally hashes the key to 256 bits). Longer keywords provide better
security than short ones, since they are less likely to be discovered
by exhaustive search.
For a detailed description of the encryption algorithm used by ccrypt,
see the man page.
Downloading and Installing from Source
The following instructions are for compiling ccrypt from source
code; if you have downloaded one of the precompiled binary
distributions, please skip to "Downloading and Installing Precompiled
Distributions" below.
The source distribution of the current version of ccrypt can be
downloaded as a gzipped tar archive from
http://ccrypt.sourceforge.net/. You can unpack the archive with a
command such as
tar -zxf ccrypt-XXX.tar.gz
For compiling and installation, please follow the instructions in
the file INSTALL. The basic installation sequence is:
./configure
make
make check
The only non-standard configuration options are --disable-libcrypt
and --disable-emacs. Normally, ccrypt will be linked against the
libcrypt library, if available. If this library is not available,
or if the --disable-libcrypt option is given to ./configure, then
we will use our own replacement for this library. This is useful
for creating binary distributions when we don't want to distribute
libcrypt.so. The --disable-emacs configuation option can be used to
disable emacs support.
Downloading and Installing Precompiled Distributions
ccrypt is also available in precompiled formats for a number of
popular platforms, including Linux, MacOS X, and Windows under
CygWin. In each case, just install the binaries in one of the
places where the operating system usually looks for them, such as
/usr/bin. You should also create symbolic links to the ccrypt
binary named ccencrypt, ccdecrypt, and ccat; when ccrypt is invoked
by one of these names, its default behavior changes. To create the
appropriate links, change to the directory where you have installed
ccrypt, and run the commands
ln -s ccrypt ccencrypt
ln -s ccrypt ccdecrypt
ln -s ccrypt ccat
You may also want to install the man page by copying ccrypt.1 to an
appropriate directory, such as /usr/share/man/man1.
The precompiled distributions are usually prepared without
internationalization support.
Windows users see the file README-WIN.
Usage
Usage: ccrypt [mode] [options] [file...]
ccencrypt [options] [file...]
ccdecrypt [options] [file...]
ccat [options] file...
Modes:
-e, --encrypt encrypt
-d, --decrypt decrypt
-c, --cat cat; decrypt files to stdout
-x, --keychange change key
-u, --unixcrypt decrypt old unix crypt files
Options:
-h, --help print this help message and exit
-V, --version print version info and exit
-L, --license print license info and exit
-v, --verbose print progress information to stderr
-q, --quiet run quietly; suppress warnings
-f, --force overwrite existing files without asking
-m, --mismatch allow decryption with non-matching key
-E, --envvar var read keyword from environment variable (unsafe)
-K, --key key give keyword on command line (unsafe)
-k, --keyfile file read keyword(s) as first line(s) from file
-P, --prompt prompt use this prompt instead of default
-S, --suffix .suf use suffix .suf instead of default .cpt
-s, --strictsuffix refuse to encrypt files which already have suffix
-F, --envvar2 var as -E for second keyword (for keychange mode)
-H, --key2 key as -K for second keyword (for keychange mode)
-Q, --prompt2 prompt as -P for second keyword (for keychange mode)
-t, --timid prompt twice for encryption keys (default)
-b, --brave prompt only once for encryption keys
-y, --keyref file encryption key must match this encrypted file
-r, --recursive recurse through directories
-R, --rec-symlinks follow symbolic links as subdirectories
-l, --symlinks dereference symbolic links
-T, --tmpfiles use temporary files instead of overwriting (unsafe)
-- end of options, filenames follow
For detailed usage information, see the man page.
Emacs support
ccrypt comes with an emacs package for reading and writing
encrypted files. The package is called ps-ccrypt, and it is based
on the jka-compr package which is part of GNU Emacs. Unlike
previous versions of this package, it can be used in addition to,
and not instead of, jka-compr, to handle both encrypted and
compressed files. (However, files that are both encrypted and
compressed are not currently handled correctly).
To use the package, simply load ps-ccrypt and edit as usual. When
you open a file with the ".cpt" extension, emacs will prompt you
for a password for the file. It will remember the password for the
buffer, and when you save the file later, it will be automatically
encrypted again (provided you save it with a ".cpt"
extension). Except for the password prompt, the operation of the
package should be transparent to the user. The command M-x
ccrypt-set-buffer-password can be used to change the current
password of a buffer.
The simplest way to use this package is to include the lines
(setq load-path (cons "path" load-path))
(require 'ps-ccrypt "ps-ccrypt.el")
in your .emacs file, where path is the directory which holds the file
ps-ccrypt.el.
Support and Reporting Bugs
Ccrypt has a project page on SourceForge at
http://sourceforge.net/projects/ccrypt/. There you will find facilities
for reporting bugs, submitting patches, asking for support, asking for
features, or discussing ccrypt in general. You are encouraged to use
these facilities. You can also send email to the author.
Author
Copyright (C) 2000-2018 Peter Selinger <selinger at users.sourceforge.net>
License
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, 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.
GPG Key
Peter Selinger's GPG key fingerprint is:
12A2 4B3C 3790 B688 E484 7A98 A68B CC37 CA31 696A
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