When you send imported text or doc fies or folders as a atachement by mail, you need to think about security. You should use encryption techniques for your important files or folders to transferring data online or offline. ( by Mail, Upload your files some where, File or folder copied to USB etc ).
You can encrypt a single file or folder by using gpg command in Linux distributions. With this command encryption method is very easy, you need a password to decrypt a file or folder.
Now I will explain steps to encrypt or decrypt a file or folder in linux. GPG command can be found in almost all linux operating systems. I am using CentOS Linux release 7.2.1511 (Core) operating system.
Here I will create a text file named as encryption-text-file under my home directory.
Step 1: Open a terminal in your Linux distribution.
Step 2: Use following command
gpg –symmetric –cipher-algo AES256 encryption-text-file
when you will run this command , a new window will open where you can set your password as shown in below image. For your password confirmation, you have to re-enter your password.
Now file will be saved as “encryption-text-file.gpg” . Here .gpg is encryption extension. You have sucessfully encrypted your file.
Step 3: Testing of Encryption
Now I will try to open this file using linux cat command.
[root@www]# cat encryption-text-file.gpg
You will not able to read this text because it is encrypted.
Step 4: How to decrypt a file?
To decrypt a text file you have to use again gpg command as explained below.
gpg -o encryption-text-file -d encryption-text-file.gpg
When I will run this command, a new window will open, where you have put password that was used during encrption process as show below image.
Your file is sucessfully decrypted your text file. For testing you can open file using cat command as explained below.
[root@www]# cat encryption-text-file
This is test file for Encryption and Decryption test.
Tip : Please use strong passwords during encryption process.