
                                   ccrypt

   Secure encryption and decryption of files and streams
     _________________________________________________________________

  Description

   ccrypt is a utility for encrypting and decrypting files and streams.  It
   was designed to replace the standard unix crypt utility, which is
   notorious for using a very weak encryption algorithm. ccrypt is based on
   the Rijndael cipher, which is the U.S. government's chosen candidate for
   the Advanced Encryption Standard (AES, see http://www.nist.gov/aes/).
   This cipher is believed to provide very strong security.

   Unlike unix crypt, 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.

   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

   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.

   ccrypt is also available in precompiled formats for a number of
   popular platforms, including Linux, MacOS X, FreeBSD, Sun Solaris,
   AIX, 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/local/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/local/man/man1.

   Windows users see the file README.win.

   For users of the Redhat Package Manager, ccrypt is also available
   as a source RPM or binary RPM.

  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 var (unsafe)
    -K, --key key          give keyword on command line (unsafe)
    -k, --keyfile file     read keyword(s) as first line(s) from file
    -S, --suffix .suf      use suffix .suf instead of default .cpt
    -P, --prompt prompt    use this prompt instead of default
    -t, --timid            prompt twice for destructive encryption keys
    -r, --recursive        recurse through directories
    -R, --rec-symlinks     follow symbolic links as subdirectories
    -l, --symlinks         dereference symbolic links
    --                     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 jka-compr-ccrypt, and it is based
   directly on the jka-compr package which is part of GNU Emacs. It
   handles both encrypted and compressed files (although currently not
   encrypted compressed files).

   To use the package, simply load jka-compr-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 package also handles compressed ".gz",
   ".bz2", and ".Z" files, and it should be used instead of, not in
   addition to, jka-compr. 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 'jka-compr-ccrypt "jka-compr-ccrypt.el")

   in your .emacs file, where path is the directory which holds the file
   jka-compr-ccrypt.el.

  Author

   Copyright (C) 2000-2001 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., 675 Mass Ave, Cambridge, MA 02139, USA.
