mcrypt: encrypt your files

In an earlier article we explored how to encypt text files with vim. There are several ways to encrypt binaries on Linux too; using GnuPG, external tools like VeraCrypt etc. mcrypt is a similar utility that works as a frontend to libemcrypt.

Installation

To install mcrypt on Ubuntu, run:

$ sudo apt-get install mcrypt

Usage

• List the algorithms supported

  $ mcrypt --list

  We will use arcfour for our example.

• List hashing algorithms supported

  $ mcrypt --list-hash

  The hash is a digest added to an encrypted file, in order to detect corruption. We will use sha384.

• Compression options

  -z : gzip
  -p : bzip2

• Compress a file

  $ mcrypt -a arcfour -h sha384 -p webcheck.dat

  where,
  -a : algorithm to use [optional]
  -h : hashing algorithm to use [optional]
  -p : use bzip2 compression [optional]
  mcrypt will prompt you for the key (or password).
  The file is saved as webcheck.dat.bz2.nc.

• Decrypt the above file

  $ mcrypt -d webcheck.dat.bz2.nc
  OR
  $ mdecrypt webcheck.dat.bz2.nc

  Extract the bz2 archive to get the original file

  $ bunzip2 webcheck.dat.bz2

• Encrypt multiple files

  $ mcrypt file1 file2

• mcrypt can handle files only. To encrypt a directory archive and compress it first

  $ tar -jcvf mydir.tar.bz2 mydir/
  $ mcrypt mydir.tar.bz2

• It is possible to pass a key in the cmdline using the -k parameter or in mcrypt configuration file (~/.mcryptrc) but these are not advisable as the key is exposed.

Webpage: mcrypt