AppImage Signing

AppImage can be signed using the Open PGP standard. This ensures that the AppImage comes from the person who pretends to be the author, and ensures that the file has not been tampered with.

Key Generation

To sign an AppImage file you will need a GPG key. Use gpg2 --full-gen-key to generate a new one. You can also check the GnuPG documentation to learn more about it.

Signing

To make appimage-builder use your key to sing the resulting AppImage is enough with specifying the key id in the AppImage >> signature section as follows:

AppImage:
  sign-key: 69O7M4CCE10E0273853CDA121896X515CC81F0AD

NOTE: The private key must be available in the user keyring for GnuPG to find it. Use gpg --import private.key to do it.

Reading the signature

To check if the AppImage was properly signed execute it with the following option --appimage-signature it will print the signature, if any, to the standard output.

$ ./gnome-calculator-3.28.0-x86_64.AppImage --appimage-signature

-----BEGIN PGP SIGNATURE-----

iQIzBAABCgAdFiEEaafEzOEOAnOFPNoSGJblFcyB8KwFAl6g2B0ACgkQGJblFcyB
8KzP6g//WnCjb2HLLJ7U3muPb53py8Y5uwes7wE5w8Xbhy+ed42W6jp48cBl4O2G
cMaSJR8xH7yPvaLVWOIfDW6i7l3QUwtBfknLBdXrdlrhdMNzgXyQiKbwSgSfQcqi
kdaX2xFiXIYUV8e5BBZcfmKoFLNy4Lqfm2q8TICxiNiEdJ4eX5UTjfHWijmGg/pQ
yVNNNGGfhOboT71DNUiJTeffwgwbDIwHHPiuXvfRyB/h8qfIMTYv0GSM3lwNGUkO
3lN4LRkdZM9t19ZLpvR3uXt5DWlV7i5Q2uIp46pEUGJPnnneO3wM+wzo8r0e9Pur
Nm/KEA9UG7Lfk6ktlq+e1r2pPWtaPwZCk3A//afPBymmGJACzvbN/XitB++hE5nT
RUyRDiFW7BWMx9mWbdXaLEfR1ZOAY5rR/QJA6bKC4IvPSvHWUwYMkJdQV+MTZ0JL
vCao5EtP6FgM0+Hm4dYoSReMK+9IpzIeg8uf8fgcaHa9lMZVryeJzmiR1vx5zu7Z
1DrDuMrqSyQ10wBBIKA7K8oJKOhrc+yNcCK8ldpYcDi4WVnvsb1ffKAKz8SdqI7/
RXwkbISmSkloDXkTRlZKW7Kwkj4spJzUEsKsDwif9C4A3lGJw2xj4pAqHlLH1uq9
u07mp5HT1wPtfoBFSXqX3MVLSzb6x4Qz1gzVXgWnhx5C5/K0L+8=
=Eruk
-----END PGP SIGNATURE-----