KarkomaOnline

There is a tool called chattr that allows you to change/set file attributes on a GNU/Linux second extended (ext2) filesystem.

For example to protect myfile.txt, proceed as follows…

chattr +i myfile.txt

A file with the “i” (immutable) attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. Only the superuser or a process pessessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

GnuPG is the GNU Privacy Guard, the open source equivalent to Pretty Good Privacy (PGP). You can use GnuPG to encrypt and/or sign your mails or files and hence transmit them in a more secure fashion and ensure their integrity.

There are graphical environments to handle GnuPG but here we are going to use text-based commands.

First of all me must generate a key pair:

gpg –gen-key

The first time you run this command it will create some directories and files, so you need to launch the command again to create the keyrings.

When prompted select these options:

DSA and ElGamal
Keysize 1024
Expire time 0 (never expires)
Personal info
Passphrase

For the moment accepting default values is fine. Be careful with your passphrase as it will be used to encrypt/decrypt and sign your data, so do not simply choose the first silly words you guess

Once you have your key-pairs, you are ready to start using GnuPG.

gpg -ea -r karkoma myfile.txt

Encrypts myfile.txt using karkoma’s public key with an ASCII armor (more on this in my next article).

gpg -d myfile.txt.asc >myfile.txt

Decrypts myfile.txt.asc (enter your passphrase)

gpg –clearsign -a myfile.txt

Signs myfile.txt. Once signed, the smallest modification to the file will indicate an invalid signature.

gpg –verify myfile.txt.asc

Verifies your file signature.

gpg -ba myfile.tar.gz

Signs a binary file

That’s all folks, just for now. I am preparing a more complete article regarding GnuPG, so come back soon.