I need to be able to encrypt/decrypt a single text file stored on my external HD in 12.04 LTS, preferably a GUI application, if any, or the command line otherwise. Thank you.
A simple way to encrypt a single file is with
This will prompt you for a passphrase, which you will need to enter later when decrypting the file.
To make this "graphical" you could put it in a
http://stackoverflow.com/questions/2811528/can-i-use-my-ssh-public-key-to-decrypt-a-file Is a question on a related subject. You can use the same principles for encryption if I am not mistaken.
Lets assume that a person wants to encrypt a file called 'message.txt':
1. Encrypting a file using GPG, for personal use
I. Using a passphrase to encrypt the file (and not the private key)
I.i. The command:
I.ii. If you want to generate an ASCII encrypted file, which is base64(i think) of that file, you can use
II. Using a private key to encrypt a file
II.i. If you want to encrypt a file using your key, instead of only a passphare, use the command
II.ii. Point II.i would give you a binary file. If you want to get an ASCII file, use --armor.
2. Decrypting the file encrypted with GPG
To decrypt, the file, use the command