GnuPG (GPG)
The gpg tool can be used to encrypt files, using a passphrase, which is like a password. It can also be used to sign something. For instance, GitHub allows you to sign your commits using GPG keys.
To encrypt something, you could do this. It will generate a file.gpg
$ gpg --cipher-algo AES-256 --symmetric file
And, to decrypt (no passphrase is asked if it is cached)
$ gpg -d file.gpg
# generate back your file
A private key can be used instead of a passphrase. To decrypt a file that was encrypted using a private key:
$ gpg --import xxx.key [...]
🔐 To crack a gpg encrypted file, refer to password brute force.
👻 To-do 👻
Stuff that I found, but never read/used yet.
- PGP (Pretty Good Privacy). GnuPG/GPG = implementation from the GNU project.