UNIX File Encryption howto

Q. I’m using UNIX (FreeBSD) at work. I need to encrypt a file. What command I need to type?

A. You need to use crypt command which provides very simple file encryption. It works under UNIX, BSD, Linux and possible all other UNIX like oses.

Itis a very simple encryption program, working on a secret-key basis. It operates as a filter, i.e., it encrypts or decrypts a stream of data from standard input, and writes the result to standard output. Since its operation is fully symmetrical, feeding the encrypted data stream again through the engine (using the same secret key) will decrypt it.

Task: Encrypt the original file called my.txt

Type the command as follows:
$ cat my.txt | crypt > my.cpy
Output:

Enter key:

This will create an encrypted form of my.txt file, and store it in the file my.cpy.

Task: Ensure that the file is encrypted

Type the following command:
$ cat my.cpy

Task: Decrypt the file called my.txt

Type the command as follows:
$ cat my.cpy | crypt > my.file.txt

Under FreeBSD you can use enigma (same command with different name - the crypt utility, also known as enigma), to displays the previously created file on the terminal:
$ enigma PASSWORD < my.cpy

Also note that many new UNIX oses comes with mcrypt command. It is intended to be a replacement of the old unix crypt under the GNU General Public License.