hOW tO eNCRYPT aND dECRYPT fILES wITH a pASSWORD

To encrypt and decrypt files with a password, use gpg command. It is an encryption and signing tool for Linux/UNIX like operating system such as FreeBSD/Solaris.

GnuPG stands for GNU Privacy Guard and is GNU's tool for secure communication and data storage. It can be used to encrypt data and to create digital signatures. It includes an advanced key management facility.
Encrypting a file in linux

To encrypt single file, use command gpg as follows:
$ gpg -c filename

To encrypt myfinancial.info file, type the command:
$ gpg -c myfinancial.info
Output:

Enter passphrase:
Repeat passphrase:

This will create a myfinancial.info.gpg file.
Option:

* -c : Encrypt with symmetric cipher.

Caution if you ever forgot your password aka passphrase, you cannot recover the data as it use very strong encryption.
Task: decrypt file

To decrypt file use gpg command:
$ gpg myfinancial.info.gpg
Output:

gpg myfinancial.info.gpg
gpg: CAST5 encrypted data
Enter passphrase:

Decrypt file and write output to file vivek.info.txt you can run command:
$ gpg myfinancial.info.gpg –o vivek.info.txt

Remember if file extension is .asc, it is a ASCII encrypted file and if file extension is .gpg, it is a binary encrypted file.