I’ve been meaning to spend a bit of time looking at use cases for gpg
I wasn’t aware that you don’t even need to set up any accounts. You can start using for symmetric encryption right out of the box. Symmetric encryption relies on a shared password / passphrase that is shared with recipients.
I’m using a fairly fresh installation of mxlinux in Virtual Box. GnuPG is already installed as with pretty much any distro.
As you can see below, lots of options are available.
simon@mx:~
$ gpg -h
gpg (GnuPG) 2.2.12
libgcrypt 1.8.4
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Home: /home/simon/.gnupg
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2
Syntax: gpg [options] [files]
Sign, check, encrypt or decrypt
Default operation depends on the input data
Commands:
-s, --sign make a signature
--clear-sign make a clear text signature
-b, --detach-sign make a detached signature
-e, --encrypt encrypt data
-c, --symmetric encryption only with symmetric cipher
-d, --decrypt decrypt data (default)
--verify verify a signature
-k, --list-keys list keys
--list-signatures list keys and signatures
--check-signatures list and check key signatures
--fingerprint list keys and fingerprints
-K, --list-secret-keys list secret keys
--generate-key generate a new key pair
--quick-generate-key quickly generate a new key pair
--quick-add-uid quickly add a new user-id
--quick-revoke-uid quickly revoke a user-id
--quick-set-expire quickly set a new expiration date
--full-generate-key full featured key pair generation
--generate-revocation generate a revocation certificate
--delete-keys remove keys from the public keyring
--delete-secret-keys remove keys from the secret keyring
--quick-sign-key quickly sign a key
--quick-lsign-key quickly sign a key locally
--sign-key sign a key
--lsign-key sign a key locally
--edit-key sign or edit a key
--change-passphrase change a passphrase
--export export keys
--send-keys export keys to a keyserver
--receive-keys import keys from a keyserver
--search-keys search for keys on a keyserver
--refresh-keys update all keys from a keyserver
--import import/merge keys
--card-status print the card status
--edit-card change data on a card
--change-pin change a card's PIN
--update-trustdb update the trust database
--print-md print message digests
--server run in server mode
--tofu-policy VALUE set the TOFU policy for a key
Options:
-a, --armor create ascii armored output
-r, --recipient USER-ID encrypt for USER-ID
-u, --local-user USER-ID use USER-ID to sign or decrypt
-z N set compress level to N (0 disables)
--textmode use canonical text mode
-o, --output FILE write output to FILE
-v, --verbose verbose
-n, --dry-run do not make any changes
-i, --interactive prompt before overwriting
--openpgp use strict OpenPGP behavior
(See the man page for a complete listing of all commands and options)
Examples:
-se -r Bob [file] sign and encrypt for user Bob
--clear-sign [file] make a clear text signature
--detach-sign [file] make a detached signature
--list-keys [names] show keys
--fingerprint [names] show fingerprints
Please report bugs to <https://bugs.gnupg.org>.Now, we’ll take a man page (uptime as it’s nice and short) and save it to a file ready to encrypt and email to test encryption.
simon@mx:~
$ man uptime > uptime.txtsimon@mx:~
$ gpg --armor --symmetric uptime.txtWe could save some keystrokes by just typing gpg -ac <filename>
You’ll be prompted for a password (which you have to enter twice), I chose simonh
As you can see, gpg also compresses the encrypted file (uptime.txt.asc).
simon@mx:~
$ ll
total 300K
-rw-r--r-- 1 simon simon 113 Apr 17 18:18 dead.letter
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:17 Desktop
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 Documents
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 Downloads
drwx------ 2 simon simon 4.0K Apr 16 15:36 mail
drwx------ 5 simon simon 4.0K Apr 16 17:26 Maildir
-rw------- 1 simon simon 467 Apr 19 18:26 mbox
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 Music
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 Pictures
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 Public
drwxr-xr-x 3 simon simon 4.0K Apr 17 17:53 src
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 Templates
-rw-r--r-- 1 simon simon 1.9K May 20 16:52 uptime.txt
-rw-r--r-- 1 simon simon 1.4K May 20 16:52 uptime.txt.asc
drwxr-xr-x 12 simon simon 4.0K May 9 20:00 var
drwxr-xr-x 2 simon simon 4.0K Apr 15 19:25 VideosHere is the (encrypted) contents of the uptime man page:
simon@mx:~
$ cat uptime.txt.asc
-----BEGIN PGP MESSAGE-----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=WzQF
-----END PGP MESSAGE-----We’ll email it to ourselves now, read the email and save the message in the body to uptime
simon@computer:~$ gpg -d uptime > uptime-manualOf course, you’ll be prompted for the password simonh and you get the original file back.
Here’s the original, decrypted text
UPTIME(1) User Commands UPTIME(1)
NAME
uptime - Tell how long the system has been running.
SYNOPSIS
uptime [options]
DESCRIPTION
uptime gives a one line display of the following information. The current time, how long
the system has been running, how many users are currently logged on, and the system load
averages for the past 1, 5, and 15 minutes.
This is the same information contained in the header line displayed by w(1).
System load averages is the average number of processes that are either in a runnable or
uninterruptable state. A process in a runnable state is either using the CPU or waiting
to use the CPU. A process in uninterruptable state is waiting for some I/O access, eg
waiting for disk. The averages are taken over the three time intervals. Load averages
are not normalized for the number of CPUs in a system, so a load average of 1 means a sin‐
gle CPU system is loaded all the time while on a 4 CPU system it means it was idle 75% of
the time.
OPTIONS
-p, --pretty
show uptime in pretty format
-h, --help
display this help text
-s, --since
system up since, in yyyy-mm-dd HH:MM:SS format
-V, --version
display version information and exit
FILES
/var/run/utmp
information about who is currently logged on
/proc process information
AUTHORS
uptime was written by Larry Greenfield ⟨greenfie@gauss.rutgers.edu⟩ and Michael K. Johnson
⟨johnsonm@sunsite.unc.edu⟩
SEE ALSO
ps(1), top(1), utmp(5), w(1)
REPORTING BUGS
Please send bug reports to ⟨procps@freelists.org⟩
procps-ng December 2012 UPTIME(1)So, just using this simple method, you can take any file, encrypt it (you can change the cipher by the way), compress it and then send it to someone who knows the key. If you accidentally send the message to someone who wasn’t expecting it, they’ll have little clue what it’s all about.
Awesome!