How can I sign a file with an alternate key

Question

I have two keys in my keyring:

jason@host $ gpg --list-keys
/home/jason/.gnupg/pubring.gpg
------------------------------
pub   1024R/B051EDBF 2017-11-27
uid                  realname <[email protected]>
sub   1024R/4C83269B 2017-11-27

pub   1024R/28FDD919 2017-11-27
uid                  anothername <[email protected]>
sub   1024R/4C928D6B 2017-11-27

I can sign a file with it

jason@host $ gpg --sign example

And I can verify that signature

other@host $ gpg --verify ~jason/example.gpg

As the user "jason" how do I sign that file instead with the second key in the keyring?

(Note that I am using 1024 bit keys because they generate more quickly. This is POC work and will not be exposed to the internet.)

Answer 1

You specify a different default secret key. See section 1.2.1 of the GnuPG documentation.

gpg --default-key 28FDD919 --sign example

You can also change the default key in the GPG configuration file to make it persistent.

default-key 28FDD919

As a side-note, RSA 1024 is obsolete now days and is weak. 2048 is the recommended minimum.